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CONTENTS
ViewpointAPEC, PCIM, Three Big Events Coming Soon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Industry NewsFormation of 5S Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Emerson to Acquire Artesyn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Corporate Vice President Back-End Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
SiC License Between APT & Northrop Grumman . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Maxwell Appoints Michael Liedtke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Fairchild Experts at APEC 2006 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
World’s Smallest Charger IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Filling the “Experience Gap” with Modules, Dave B. Bell, President, Linear Technology Corporation . . . . . . . . . . . . . . . . . . . . . . . .12
MarketwatchGetting Sexier Every Year? , Chris Ambarian, iSuppli Corporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
TechTalkEnergy Savings and Low Cost Are Our Goal , Interview with Doug Bailey, Power Integratioins, By Liu Hong, editor Power Systems
Design China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Cover StoryAdvances in Brightness Control Technology, Roger Holliday, VP Strategic Business Development, Microsemi Corporation . . . . . .18
FeaturesPower Management—Advances in Power Management, Paul Greenland, and Werner Berns, National Semiconductor . . . . .24
Power Conversion—Optimizing Step-Down Converter Applications, Thomas Schaeffner, Texas Instruments . . . . . . . . . . . . .28
Power Management—Getting You Power, Guido Körber, Code Mercenaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Power Supply—Complete 10A DC/DC Converter, Afshin Odabaee, PME, Power Management Products,
Linear Technology Corporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Power Generation—Thermoelectric Generator, Mieke Van Bavel, IMEC, Leuven . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Power Control—Intelligent Lighting Saves Power, Ofer Aluf , Technical Sales Manager, Future Electronics Europe . . . . . . . . . . .45
Portable Power—Dynamic Power Control for Power Amplifiers, Lei Feng, Senior Strategic Applications Engineer, Micrel Inc. . .48
New Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51-56
Member Representing
Eric Carroll ABB SwitzerlandArnold Alderman AnagenesisHeinz Rüedi CT-Concept TechnologyClaus Petersen DanfossDr. Reinhold Bayerer eupecChris Rexer Fairchild SemiconductorDr. Leo Lorenz Infineon TechnologiesDavin Lee Intersil Eric Lidow International RectifierDavid Bell Linear Technology
Member Representing
Rüdiger Bürkel LEM ComponentsRalf J. Muenster MicrelPaul Greenland National SemiconductorKirk Schwiebert OhmiteChristophe Basso On SemiconductorBalu Balakrishnan Power IntegrationsDr. Thomas Stockmeier SemikronUwe Mengelkamp Texas InstrumentsPeter Sontheimer Tyco Electronics
Power Systems Design Europe Steering Committee Members
PowerSystems DesignE U R O P EPowerSystems DesignE U R O P E
2 Power Systems Design Europe March 2006
I am ready to go to Dallas and meet oldfriends in the power family and enjoy the begin-ning of spring in Texas at APEC followed quick-ly in May by PCIM China in Shanghai and inMay by PCIM Europe in Nuremberg. Just nowwhile I am sitting typing the Viewpoint, it is stillsnowing and a nice white cover is down like ablanket here at my place at the Baltic Sea.
Healthy industrial environment in Europe andelsewhere is the platform for stable growth inpower electronics. The European market isfocused on industrial, automotive and telecomproducts.
As a tradition at PCIM Exhibition inNuremberg I will moderate a PodiumsDiscussion each day. Experts from the indus-try will present their position and have opendiscussions in the auditorium. The topics fordiscussions are as follow:“Gate Drivers optimized for MOS Devices” willbe topic on Tuesday.“Digital Power and the application focus” willhighlight Wednesday’s discussions.“Passive Components are the Spices in Design”will be on Thursday.
I decided on this set of topics to complementthe PCIM conference subjects.
So Nuremberg will be a focal point to meetand chat about power and its elements. Pleasestay tuned for updates on the final time andschedule for the daily podium discussions.
In the current issue we focus on portablepower. Portability is what the customer is look-ing for. Modern technology for batteries andcapacitors create solutions that match therequests for performance. Power Managementby chip and system level is a mandatory sub-ject for any electronics.
The cover story supplied by Microsemi tellsus about brightness control on displays in auto-motive applications. We can understand auto-mobiles as being a big portable product thatneeds to be efficient in power.
Texas Instruments explains a step-down converter to be optimized for small space. Small space is the important factor for portableapplications.
Getting power supply off a USB port isdetailed expressed by Code Mercenaries.
IMEC does research to use human bodyheat for power generation—a look into futuresolutions.
As we see, most of the efficiency enhance-ments have been stimulated by device improve-ment. The electronic switches have becomebetter in respect to conduction and switchinglosses.
Silicon Carbide SiC is the material of choicein real applications. We have seen SiC diodesused in power supplies to enhance efficiency.APT and Northrop Grumman will work togeth-er to manufacture next-generation silicon car-bide (“SiC”) microelectronic devices—a stepto commercial success for SiC.
The most important switch is still the MOS-FET and we are looking forward to seeing whatSiC can do for active switches. The ECPE userforum in Nuremberg in mid-March will generateus some more insight as to what SiC hasachieved and what will be practical for the nextgeneration of applications.
All details for the power events are listed onpage 6 in this issue. If you are around duringthese events please stop by at our booth tohave a chat.
Best regards,
Bodo ArltEditorial DirectorThe Power Systems Design Franchise
AGS Media Group
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Phone: +49 4343 421790
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www.powersystemsdesign.com
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Editor-in-Chief Power Systems Design China Liu [email protected]
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Registration of copyright: January 2004
ISSN number: 1613-6365
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Volume 3, Issue 2
VIEWPONIT
APEC, PCIM, Three BigEvents Coming Soon
4 Power Systems Design Europe March 2006
INDUSTRY NEWS
Formation of 5S Components
ON Semiconductor announced theappointmABB Switzerland Semiconductorsand ABB Semiconductors announce the for-mation of 5S Components, headquartered inPittsburgh, PA. In a management buy-outgeared to giving semiconductor salesstronger focus, John Siefken (right) andKenny Stephenson (center) purchased the
business of ABB Semiconductors Inc fromABB Switzerland/Semiconductors, effectiveDecember 1, 2005 making 5S Componentsthe successor to ABB Semiconductors Inc.Additionally, ABB Switzerland/Semiconductorshas entered into an agreement with 5SComponents to be the exclusive distributor ofABB Switzerland/Semiconductor products in
North America. 5S Components will continuethe business of ABB Semiconductors at thesame location, with the same address andtelephone numbers as before. Most of the ABBSemiconductor employees transferred to 5S.
Kurt Hörhager, Managing Director of ABBSwitzerland/Semiconductors comments that“Creating 5S guarantees focus on semicon-ductor sales in North America, a vital part ofour growth strategy. John, Kenny and the 5Steam have my full backing and ABB will beable to support the North American marketand its customers even better than in thepast”. Roland Villiger (left), VP of Sales &Marketing adds, “We are working with 5S toinsure a smooth transition and an uninterrupt-ed flow of products. This change will in noway impact the quality and dependability ofthe support that customers have alwaysreceived: they can expect the same servicefrom 5S and the ABB factories now as theypreviously received because the teamremains the same”.
www.abb.com/semiconductors
Emerson and Artesyn Technologiesannounced that Artesyn will become part ofEmerson Network Power. Emerson will acquireArtesyn for $11 a share in cash (approxi-mately $500 million net of acquired cash)pending customary regulatory approvals andapproval by Artesyn shareholders.
The agreement brings additional embeddedpower conversion technologies to EmersonNetwork Power's existing portfolio of solu-tions for customers in the enterprise comput-ing, data, and telecommunications industries.Artesyn provides leading original equipmentmanufacturers (OEMs) with advanced power
conversion equipment as well as hardwareand software subsystems for a range of communication applications.
Emerson to Acquire Artesyn
www.emersonnetworkpower.com
STMicroelectronics announced theappointment of Jeffrey See as CorporateVice President and General Manager of ST’sworldwide back-end operations.
Jeffrey See, currently General Manager ofthe ST ‘s manufacturing complex in Ang MoKio (Singapore) is promoted to the position ofCorporate Vice President, Central Back-EndGeneral Manager, effective April 3, 2006.See’s appointment follows the departure ofGiordano Seragnoli, the current CorporateVP for back-end activities who, at 69, is leav-
ing for a well deserved retirement at the endof Q2, 2006.
A respected veteran of semiconductorindustry, See (born in Singapore in 1945) hasplayed a vital role in establishing and growingthe Company’s state-of-the-art manufacturingoperations in the Asia Pacific region, wherethe largest part of ST’s assembly and testproduction is also located.
Jeffrey See has been with the Companysince it started its operations in Singapore in1969 when he joined it as a Quality Assurance
Supervisor for ST’s first Assembly and Testoperation in Toa Payoh, becoming Deputy PlantManager in 1980. In 1983, he was appointedto set up the region’s first wafer fabricationplant in Ang Mo Kio, which has grown underhis leadership to become the single largestvolume-manufacturing facility within ST. Today,ST’s Ang Mo Kio manufacturing complex withthree plants and a staff of 5400 represents aglobal benchmark for achievements in quali-ty, cost, and cycle time.
Corporate Vice President Back-End Manufacturing
www.st.com
www.artesyn.com
Europe Sales Offices: France 33-1-41079555 Italy 39-02-38093656 Germany 49-89-9624550 Sweden 46-8-623-1600 UK 44-1628-477066 Finland 358-9-88733699 Distributors:Belgium ACAL 32-0-2-7205983 Finland Tech Data 358-9-88733382 France Arrow Electronique 33-1-49-784978, TekelecAirtronic 33-1-56302425 Germany Insight 49-89-611080,
Setron 49-531-80980 Ireland MEMEC 353-61-411842 Israel AvnetComponents 972-9-778-0351 Italy Silverstar 39-02-66125-1Netherlands ACAL 31-0-402502602 Spain Arrow 34-91-304-3040Turkey Arrow Elektronik 90-216-4645090 UK Arrow Electronics 44-1234-791719, Insight Memec 44-1296-330061
6 Power Systems Design Europe March 2006
INDUSTRY NEWS
Power Events
• APEC 2006, March, 19 - 23, Dallas TX,www.apec-conf.org
• PCIM China 2006, Mar. 21 - 23, Shanghai www.pcimchina.com
• PCIM Europe 2006, May 30 - June1,Nuremberg, www.pcim.de
• SMT/HYBRID 2006, May 30 - June1, Nuremberg, www.mesago.de
• SENSOR/TEST 2006, May 30 - June1,Nuremberg, www.sensor-test.de
• EPE-PEMC 2006, Aug 30 - Sep 1, Portoroz,Slovenia, www.ro.feri.uni-mb.si/epe-pemc2006
• MICROSYSTEM, October 5 - 6 , Munich,www.mesago.de
• ELECTRONICA 2006, Nov. 14 - 17, Munich,www.electronica.de
• SPS/IPC/DRIVES 2006, Nov. 28 - 30,Nuremberg, www.mesago.de
Fairchild Semiconductor’s power expertswill offer techniques for developing power effi-cient designs and profile the leading edgeproducts that make them possible at the 2006Applied Power Electronics Conference andExposition (APEC), held March 19 – 23 inDallas, Texas. Fairchild’s booth #63 will bestaffed by motor, lighting, DC/DC and AC/DCpower experts from the Global PowerResource who will offer solutions to designand power application challenges.
Fairchild technologists will present papers atthe conference. The Global Power Resourceis an integral element of Fairchild’s delivery ofhighly integrated products for the consumer,communication, industrial, computing andautomotive market. The Global PowerResource encompasses a worldwide networkof design centers, staffed with system designexperts, who partner closely with customers tooptimize and develop innovative designs.
Additionally, Fairchild has implemented design,selection and educational tools into its website (http://www.fairchildsemi.com/designcen-ter) to assist customers in the power optimiza-tion of their design at their convenience.
APEC, the Applied Power ElectronicsConference and Exposition, is the leadingevent worldwide for practicing power electronicsprofessionals, focused on the practical andapplied aspects of the power electronics business.
Fairchild Experts at APEC 2006
www.fairchildsemi.com
Advanced Power Technology announcedthat the company has entered into a licenseagreement with the Electronic Systems’ sec-tor of Northrop Grumman to manufacturenext-generation silicon carbide (“SiC”) micro-electronic devices.
This agreement forms an exclusivefoundry supplier relationship wherebyNorthrop Grumman will license certain SiCtechnology to Advanced Power Technologyincluding relevant SiC patents and manufac-turing methods to enable Advanced PowerTechnology to manufacture proprietary highperformance SiC microelectronic devicesexclusively for Northrop Grumman. In addi-
tion, the agreement allows Advanced PowerTechnology to use the licensed technology tomanufacture and sell other high performanceSiC devices for commercial purposes. Bothcompanies possess substantial expertise inSiC technology and view SiC based powersemiconductors as strategically important toa wide array of next generation applications.
The driving force for the adoption of siliconcarbide for military as well as civilian applica-tions is the need to reduce weight and size ofpower control and management systems andtheir associated support equipment, in partic-ular cooling systems and heat dispersingpackaging. SiC semiconductors have demon-
strated large performance advantages innumerous test beds over the most advancedsilicon components.
Military applications include radar, hybridpower systems, electric power control anddistribution, electronic jamming, and wide-band communications systems.
Potential non-military applications that canbenefit from silicon carbide’s military-levelperformance include hybrid vehicles, electricpower transmission, computer/servers, med-ical systems, and alternative energy.
SiC License Between APT & Northrop Grumman
www.advancedpower.com
www.northropgrumman.com
MaxwellTechnologiesannounced that ithas appointedMichael J. Liedtkevice president,business develop-ment, with primaryresponsibility forestablishing andmaintaining strate-gic relationshipswith major original
equipment manufacturers (OEMs) to promoteultracapacitor-based solutions for industrial andtransportation applications.
Liedtke, 45, has spent the past eight yearsas director of marketing and transportationdesign management for BMW’s California-based DesignworksUSA. Previously he held aseries of auto, truck and bus design and projectmanagement positions with DaimlerChrysler’sMercedes Benz division in Stuttgart, Germany,and its Freightliner truck division in Portland,Ore. He also spent more than four years in theaerospace industry with McDonnell Douglas
and Boeing, where he held various engineeringand research and development positions. Heholds joint U.S. and German citizenship and isfluent in English, German and French.
Liedtke was born to German parents in theU.S., but was raised and educated in Germanybefore returning to the U.S. for most of his pro-fessional career. He holds a Master of Sciencedegree in mechanical engineering from theUniversity of Karlsruhe in Germany.
Maxwell Appoints Michael Liedtke
www.maxwell.com
8 Power Systems Design Europe March 2006
Summit Microelectronics announcesthe first product in a family ofProgrammable Li-Ion Charger
IC’s aimed at the latest portable con-sumer applications. Specially designedto operate with the popular UniversalSerial Bus (USB™) and other current-limited power sources, the SMB135 revolutionizes single cell Li-Ion battery charging.
Combining switch-mode operationwith Summit’s proprietary TurboCharge™ mode, the SMB135 dramati-cally cuts charge time, shrinking or elim-inating costly and bulky AC/DC “wall-wart” power supplies. Additionally theSMB135 eliminates power cables andconnectors by allowing standardizationto a single mechanical connector (USB)for power and data. By addressing the
major drawbacks of conventional solu-tions, namely charge time, power dissi-pation and solution size, the SMB135enables new standards for performance,mobility and convenience in portableconsumer electronics.
FeaturesThe SMB135 comprises a 1A current-
mode step-down (buck) switching bat-
Provides 750mA from a 500mA USB port, slashing charge time by 66% and cutting power dissipation by 90%,
versus linear chargers
10 Power Systems Design Europe March 2006
tery charger including a fully program-mable algorithm for single-cell Li-Ionand Li-Polymer cells. All chargingparameters—pre-charge/fast-charge/charge termination current, cell float/pre-charge voltage, battery tempera-ture/timer safety limits—are configurablevia the I2C/SMBus interface enabling awide variety of algorithms without hard-ware changes. The programmable algo-rithm combined with the inherent currentmultiplication effect of the switching regulator enables Summit’s TurboCharge™ mode that delivers up to750mA charging current from a standard500mA USB port (up to 1A from anAC/DC adapter). This represents morethan double the charge current typicallyavailable from competing solutions, cutting the battery charge time by asmuch as 66%.
The SMB135 can be programmedeither dynamically (real-time usingvolatile registers), by a microcontrollerand software via the I2C/SMBus port, orstatically (pre-programmed using non-volatile registers). If the static program-ming mode is used there is no need forsoftware to access the I2C/SMBus inter-face and the SMB135 functions inde-pendently as a customized but paramet-rically fixed solution.
Additionally the SMB135’s switch-mode operation provides another majoradvantage, reducing power dissipationby as much as 90% compared to com-peting linear-mode charger IC’s. Thischaracteristic has a dual benefit—dra-matically reduced power dissipationeliminates the need for “thermal currentfoldback” circuitry of competing linearsolutions, which unnecessarily extendscharge time. Also reduced power dissi-pation allows the SMB135 to be pack-aged in a tiny 1.3mm x 2.1mm chip-scalepackage (CSP)—the world’s smallest fora battery charger IC. Linear chargersolutions are typically offered in largepackages that have high power dissipa-tion capacity and require extra PCB cop-per “flood” areas for heatsinking.
The SMB135 operates from a +4.35Vto +6.0V input making it ideally suitedfor either USB or AC adapter power
sources. However for applicationswhere the AC adapter may be poorlyregulated and/or an aftermarket productthe SMB135 will tolerate +10V inputswithout damage. Switching frequency isprogrammable between 750kHz and1.25MHz providing for small externalpassive component size and cost.Ensuring long battery life when not connected to a DC power source, thereverse leakage current is less than2μA. Also when not using the I2C/SMBusport for charge control/monitoring theSMB135 provides a 500mA/100mAcontrol pin for USB compliance and aSTATUS output to drive an LED.
Enhancing reliability the SMB135 integrates over-voltage, short-circuit and thermal protection circuits. Also the SMB135 protects the battery packwith a programmable battery tempera-ture sensor and charge timers to pre-vent dangerous charging conditions.Furthermore, to protect deeply dischargedcells, the SMB135 has a 3mA “tricklecharge” mode below 2.0V. This modeallows safe, controlled recovery of the deeply discharged cell until it can accept normal charging currents.Finally the SMB135’s programmabilityenables future battery upgrades whilepreserving safety.
ApplicationsThe SMB135 is well suited to hand-
held consumer electronics devices suchas 2.5G/3G phones, PDAs/smart-phones, Bluetooth headsets, portablemedia players (PMP), portable gameconsoles, digital still cameras (DSC)/camcorders (DCC) and GPS terminals.In particular it is the ideal battery charg-ing solution for applications that use asingle USB connector to provide bothdata and power.
Design Software and Programmer forPrototype Development
To speed user product development,Summit offers customers the SMB135EVcompanion evaluation board and agraphical user interface (GUI) softwareso designers can quickly see the fea-tures and benefits and design a proto-type power supply with the SMB135.This is a complete development tool
that lets designers easily manipulate the characteristics of their systems. TheSMB135EV design kit includes menu-driven Microsoft Windows® graphic userinterface (GUI) software to automateprogramming tasks and also includes allnecessary hardware to interface to theparallel or USB port of a laptop or PC.
Once a user completes design andprototyping, the SMB135EV automati-cally generates a HEX data file that can be transmitted to Summit for reviewand approval. Summit then assigns aunique customer identification code tothe HEX file and programs the customer’sproduction devices prior to final electri-cal test operations. This ensures thatthe device will operate properly in theend application. The design kit softwarecan be downloaded today fromSummit’s website.
www.summitmicro.com
12 Power Systems Design Europe March 2006
There are a number of marketdynamics within the power elec-tronics industry that are converg-
ing to create a perplexing problem. Tobetter understand what is happening,one simply has to look to the increasingcomplexity and performance require-ments of power systems, as well as theintensity of time-to-market pressures. Atthe same time, the number of competentand seasoned power systems designerswithin the industry is diminishing.
During the last couple of decades universities have churned out graduatesskilled in digital design techniques, whilesimultaneously producing fewer gradu-ates capable of complex analog design.These factors have contributed to thegrowing “experience gap” within thepower electronics industry. As a result ofthis gap, many systems are introducedlate into the marketplace, and also havepoorly designed power systems.
Some markets, like high volume con-sumer products such as cellular phonesand video games, can justify the engi-neering effort to create a low, cost effec-tive total solution. Companies canassign a team of analog designers tooptimize their design for good systemperformance while also shaving penniesfrom the overall cost, because theextremely high volume manufacturingvolumes associated with such productseasily justifies the effort. However, mostelectronic products cannot justify thislevel of attention. In fact, it is becomingincreasingly common that companiescannot locate a qualified engineer withintheir organizations to design the powersystem for their new products.
An Alternate RouteOne straightforward and immediate
solution that companies can readilyadopt to address this decline in the
availability of power systems designexpertise is to use an off-the-shelfDC/DC converter module. In so doing,they can minimize risk, reduce the num-ber of component types purchased, andeven reduce product development time.
Telecom power systems have usedDC/DC modules for many years.Usually, these systems distribute theirpower via an intermediate 24V or 12Vbus. However, most telecom subsys-tems do not use the 24V or 12V busdirectly, but require DC/DC conversionfrom this bus voltage to the subsystemoperating voltage. Therefore, a DC/DCconverter module is used to convertfrom 24V or 12V to 2.5V, or an evenlower one, from which the subsystemcan then draw its power. These DC/DCmodules are supplied by numerous ven-dors and have standard footprints andmechanical packages, making them aquick-to-apply solution. This not onlysaves on engineering time but enables afaster time to market.
This same method of DC/DC conver-sion can be readily utilized in any powersystem, therefore enabling a simple,
quick and practical solution with minimalengineering resource. This helps com-panies with limited power system designexpertise to bridge the “experience gap.”
Some of the key advantages ofDC/DC converter modules can be sum-marized as follows:• Modules with internal input and output
capacitors are relatively insensitive toPCB layout, being just as easy to useas linear regulators. This means thatperformance can be ensured withoutan ideal PCB layout.
• Because of the very tight componentplacement inside DC/DC convertermodules, EMI is also minimized. All thehigh dv/dt nodes and high di/dt tracesare located within the module, so cou-pling to external sensitive circuitry isminimized.
• Because all of the components neededto make a complete function areincluded within the module, the manu-facturer can verify conformance tospecifications despite variations in theindividual components.
Not only do modules make perfectsense for a growing segment of thepower management market, but theyalso make sense for other analog func-tions because the same “experiencegap” exists throughout the analog world.Linear Technology and other manufac-turers are releasing new DC/DC mod-ules to address this need. An exampleof such a product is Linear’s recentlyintroduced LTM4600 uModule. This is acomplete 10A switch-mode power sup-ply in a 15mm x 15mm x 2.8mm LGApackage that only needs a single exter-nal resistor to set the required outputvoltage. Developments such as this arehelping to bridge the “experience gap.”
www.linear.com
By Dave B. Bell, President, Linear Technology Corporation
14 Power Systems Design Europe March 2006
By Chris Ambarian, Senior Analyst, iSuppli Corporation
As we head into this year’s AppliedPower Electronics Conference inDallas, Texas, I am finding it quite
interesting how power semiconductorshave evolved in the last year vis-à-visthe semiconductor industry at large.
You may recall that I suggested aboutthis time last year (“A Necessary Evil?”,PSDE April 2005) that we have anopportunity before us—an opportunity totransform power semis into somethingas value-adding and sexy as the othersemiconductors are. The alternative isto continue along a path of commoditi-zation, allowing ourselves and our effortsto be considered a necessary evil.
Funny enough, what I’ve seen in the lastyear is that power semiconductors andthe “rest” of the semiconductor markethave to some extent converged on apoint in-between where they have tradi-tionally been respectively. From my per-spective anyway, power semiconductorsare gaining more and more importanceand value and respect, though maybenot quite the point of being “sexy”—while semiconductors in general havebegun to get commoditized and a littleless valuable and sexy.
Why are power semis getting sexier?
Perhaps it’s because of the tremendousamount of innovation being churned outby our industry’s designers. A wealth ofnew technologies to address the morepressing needs for energy efficiency hasbeen pouring out of the companies inthis space—hardly displaying the kind of
behavior a staid old commodity busi-ness usually displays. The power man-agement semiconductor space thesedays is like a three-ring circus—whetherit’s new materials, or new process technologies, or new digital designapproaches, or a new merger or acqui-sition, there’s plenty of action just abouteverywhere you look. And it’s not justcommodity price and delivery—if a com-pany doesn’t choose well and constantlyinnovate, their business will quickly suf-fer—just like in the rest of the semicon-ductor market. On the other hand, if acompany innovates well and provides aneeded product, there are billions of dol-lars and some of the highest profit mar-gins in the industry to be gained (justtake a look at the leading analog chipsuppliers). It doesn’t get a whole lot sexier than that.
Or perhaps power semiconductors arebecoming sexier because the worldpublic is finally becoming aware of thelimits to the amount of energy we canuse, and of the pressing need forgreater energy efficiency in our equip-
ment. This greater public awareness is making it clearer that power manage-ment semiconductors will be a signifi-cant part of the solution to our world’spower challenges. And heroes arealways sexy.
But why is the rest of the industry look-ing a little more dowdy?
For one thing, the semiconductor indus-try just isn’t growing as fast as it has inthe past. It can’t. Nothing ever growsindefinitely—the tree never grows to thesky—and certainly the semiconductorhas become so much a part of the main-stream of human life that its growthrates are now constrained by things likepopulation and GDP. (See figure 1.)This is a blessing—the fulfillment of thepotential of semiconductors—as well asa curse. Along with the ambition of get-ting into every living room and every carand every shirt pocket, you also run therisk of eventually becoming as excitingas, say, bread or tires or bed sheets orany other pervasive commodity.
For another thing, you can blame the“Moore’s Law mentality” that has drivenmuch of the non-power semiconductorindustry for decades. The relentless pur-suit of higher and higher performanceand new functionality at lower and lowerprices has made the average consumercome to expect some pretty amazingthings, and to not think twice about thelatest amazing brainchild of the some ofthe brightest engineers on the planet.Whether we like it or not, our customersare spoiled, and it takes a lot more toimpress them now.
So to the rest of the semiconductorindustry I say, “Welcome to our world.”If you want to learn some coping skillsbecause your customers are taking youfor granted a bit more, and if they don’tcare how you get it done (just get itdone), then you’ve come to the right
place. We’ve been treated like that for acouple of generations now.
On the other hand, I’m planning to reallytake some enjoyment out of watchingthe increasing importance of powermanagement in the world as it evolves
into a more energy-constrained (andwith the help of some brilliant colleagues,a more energy efficient) place. It’sabout time.
See you at APEC.
Christopher Ambarian is a senior analyst with the market research firmiSuppli Corp., El Segundo, Calif.
Contact him at [email protected]
Figure 1. Rolling 5-year semiconductor industry growth. Like all markets eventu-ally, the semiconductor industry’s growth rate has slowed, even though the mar-ket continues a healthy increase in absolute terms. (Sources: WSTS and iSuppli.)
www.iSuppli.com
MARKETWATCH MARKETWATCH
16 Power Systems Design Europe March 2006 www.powersystemsdesign.com 17
TECHTALK TECHTALK
Interview with Doug Bailey, Vice President of Marketing, Power Integrations
During the 11th China InternationalPower Supply Show held inShenzhen, China, Mr. Doug
Bailey, Vice President of Marketing forPower Integrations, talked to PSD Chinaabout Power Integrations’ two newlyintroduced IC families, the LinkSwitch®-LP family for designing the world’s simplest handset chargers, and theLinkSwitch®-XT family, targeted forpower supply applications where tightoutput is required. These ICs are thesimplest and energy efficient solutionsthat designers can choose for designingtheir power supplies.
This article is based on an interview withMr. Doug Bailey.
Fewer components means cost savings“Energy efficient, low power chargersusing an IC from the LinkSwitch-LPfamily require just 14 components—thelowest component count available forenergy efficient switched-mode charg-ers,” Mr. Bailey told PSD China.
He said that this new IC family is mainlyfor ultra low cost battery charger appli-cations. It is the simplest and most ener-gy efficient solution, being capable ofentire replacement of the unregulatedline frequency transformers. Thesechargers are commonly sold with prod-ucts such as cell phones, cordlessphones, portable audio players, shaversand other personal electronics, andtherefore are extremely price sensitive.
This family of products with its costadvantage is enabled by the simplicityof circuit design offered by a number ofPower Integrations innovations, includingClamplessTM design methodology utiliz-ing proprietary IC trimming technologyand innovative transformer construction
techniques to eliminate RCD clam circuit-ry and control of charger output voltageand current by primary circuitry to elimi-nate optical coupler and relevant com-ponents. Other innovations include anintegrated frequency jitter and uniqueFilterfuseTM input stage to achieve EMIfiltering with a single capacitor and E-ShieldTM transformer design to elimi-nate the need for a Y capacitor.
Hysteretic thermal shutdown featureremoves the need for thermal fusescommonly used in transformer baseddesign or additional components asso-ciated with RCC designs. In addition,EcoSmart® energy efficiency technologyenables compliance with all current andproposed energy standards worldwideand a universal input range enablesdesigns that can be used worldwide.Plus, an auto restart feature reducesoutput power by more than 85% whenshort circuit and open loop failuresoccur and a simple ON/OFF controlscheme eliminates the need for loopcompensation. On top of that, a highbandwidth provides fast no-overshoot
and outstanding transitive loadresponse. All these features make itpossible to reduce system cost andincrease efficiency.
“Chargers employing LinkSwitch-LP arevastly simpler than discrete designs,which typically contain dozens of com-ponents,” said Bailey. “LinkSwitch-LPalso offers integrated energy efficiencyand safety features that are eitherunavailable in discrete designs orrequire additional components anddesign effort.” He said that LinkSwitch-LP family features a 700-V power MOS-FET integrated with control and faultprotection circuitry on a single siliconchip. The chip operates across the universal input range of 85 to 265 VAC,and achieves an extremely low no-loadpower consumption of less than 150mW at 265 VAC. The simple ON/OFFcontrol scheme of LinkSwitch-LP pro-vides constant efficiency even at lightloads, enabling easy compliance withrecent efficiency standards, and offerexcellent efficiency as compared withdesigns using linear transformers.Figure 1 shows a typical application of LinkSwitch-LP.
The lowest system cost and advancedsafety features of LinkSwitch-LP familymake it a switch device with impressiveperformance and the lowest count ofexternal components, superior to lineartransformer and RCC designs, and thesimplest energy efficient replacement for linear transformer based chargers.Its typical applications include batterychargers for handsets or cordlessphones, PDAs, power tools, MP3 play-ers or portable audio equipment andshavers, and standby and auxiliarypower sources.
Compliance and Accuracy Mr. Bailey said that the IC products forlow power supply applications are growing rapidly. Power Integrations,therefore, continues to expand its highefficient and low power IC families forcharger and adapter applications. Thenewly introduced LinkSwitch-XT is tar-geted for applications in which tight reg-ulation of output voltage and current arekey design priorities. The new ICs sup-port universal input ( 85 VAC to 265VAC) range chargers and adapters withoutput levels of up to 4 watts and maybe used in open frame applications upto 9 watts (230 VAC).
He said that the simple ON/OFF controlscheme of LinkSwitch-XT enables ahigh level of efficiency even at lightloads, and reduces no-load consump-tion to less than 300 mW. The use of atransformer with a bias winding furtherreduces no-load power consumption toless than 50 mW.
LinkSwitch-XT features a 700-V powerMOSFET together with control circuitryon a single silicon die. Its integrated
safety and reliability features includehysteretic thermal shutdown for overtemperature protection, as well as autorestart for output short circuit and openloop protection. It offers replacement oflow efficient power supplies using linearline frequency transformers. TheLinkSwitch family offers a variety ofparts to meet a range of power levelsand design parameters at universalinput voltage: LinkSwitch-LP family(LNK562-564) for ultra low cost, looselyregulated power supplies up to 3 W;LinkSwitch (LNK500-501, LNK520) forloosely regulated power supplies up to3.5 W; LinkSwitch-XT (LNK362-364) fortightly regulated power supplies up to 6W; and the LinkSwitch-TN (LNK302-306) for no-isolated buck converterswith output current up to 360 mA.Typical applications include chargers for handsets or cordless phones, PDAs,digital still cameras, MP3 players orportable audio players and shavers, and power supplies for home appli-ances, industrial equipment as well asmeasurement instruments. Figure 2 is a typical application circuitry ofLinkSwitch-XT.
“With the introduction of LinkSwitch-XT,we now have a complete portfolio of lin-ear replacement,” Mr. Bailey said. “Thedesigners can choose his desired outputcharacteristics and be guaranteed anenergy efficient design with the lowestpossible cost. We have a LinkSwitchthat fits every common charger andadapter application.”
“Power Integrations’ breakthrough technology enables compact, energyefficient power supplies in a wide rangeof electronics products, including bothAC-DC and DC-DC converters. Thiscompany’s EcoSmart energy efficiencytechnology dramatically reduces energywaste, and has saved consumers andbusinesses around the world an estimatedmore than $1 billion on their electricitybills since its introduction in 1998.”
—Liu Hong, editor, Power SystemsDesign China.
Figure 1. The typical application circuitry of LinkSwitch-LP. Figure 2. The typical application circuitry of LinkSwitch-XT.
www.powerint.com
Doug Bailey, Vice President ofMarketing, Power Integrations.
18 Power Systems Design Europe March 2006
COVER STORY
Drive critical automotive display improvements
Liquid crystal display technology has proliferated rapidly throughout the electronics world, fromnotebook computers and large screen television sets to the automobile.
By Roger Holliday, Vice President Strategic Business Development, Integrated Products GroupMicrosemi Corporation
Each application imposes uniquedemands for its system design-ers. Especially demanding are the
requirements found in today’s competi-tive automotive industry. As with manynew features, the use of LCD technolo-gy in automotive displays began in luxu-ry models, where manufacturers havebeen using bright full-color displays todifferentiate their model offerings.
Dashboard navigation displays nowhave become standard features in thesehigh-end vehicles, either for GlobalPositioning System functionality or,when this capability is not customer-selected, then for other traditional vehicle and diagnostic data.
In addition to providing the means todisplay useful GPS maps, LCD displaysincreasingly are being used to commu-nicate more “driver critical” information.Typical of these premium vehicle fea-tures are traffic avoidance, rear end andblind spot monitoring via charge-cou-pled device (CCD) cameras on theirGPS displays. These provide full-motionrear-view video for added safety whenthe vehicle is moving in reverse.
Rapidly gaining popularity in high-endvans and sport-utility vehicles are rearseat full-motion video entertainment
systems using LCD screens. Comingsoon are video and wireless communi-cation systems, as well as LCD clusterdisplays that will allow drivers to cus-tomize their speedometers, tachometersand engine monitoring gauges in formatstailored precisely to their preferences.
Regardless of the specific display, inthe automotive world brightness controlis an essential design challenge thatmust be met. Unlike notebook computeror television applications, automotivedisplays have an inherent impact onowner safety and manufacturer liabilityconcerns.
The fundamental issue is the widerange of display brightness required tofunction both in broad daylight and the
dark of night. This creates a serioussafety challenge, since brightness levelsrequired for daytime viewing can effec-tively blind drivers at night.
Night driving, with its potential for“snow-blindness” (the brief vision losswhen looking from a bright light into thedarkness) is a significant danger. Evendisplay intensities as little as 20 percentabove optimal levels can threaten driversafety due to the eye’s need to readjustto the different brightness levels.
In addition, screen contrast andbrightness levels in vehicular displaysare extremely critical compared to otherconsumer applications due to the differ-ent manner in which they are used.When viewing a computer or televisiondisplay, we generally remain focused on the screen for extended periods.Drivers, on the other hand, must repeat-edly focus and refocus between thehighway ahead and their close-up dash-board displays. This rapid and frequentglancing to retrieve data and then toremain in control of the vehicle regardlessof traffic conditions necessitates well-engineered display brightness control.
As with all flat panel displays, theessential prerequisite for assuring themost readable presentation of data on
20 Power Systems Design Europe March 2006
COVER STORY
screen is having a well designed side orbacklighting. In respect to automotiveapplications today, there are two basicapproaches for achieving safe driver-viewable displays under varying lightconditions.
The first approach is simply to reversethe display contrast under software con-trol, as ambient light changes to presetlevels. Software-controlled systemsessentially toggle the backgrounds fromlight to dark, and the on-screen informa-tion from dark to light. This results in a
much lower overall luminance level tothe driver. Unfortunately, this approachhas only limited effectiveness, question-able ergonomic characteristics, and willnot work with the increasing number ofvideo-based applications.
The second approach, based on integrated circuit control, uses a wide-range cold cathode fluorescent lamp(CCFL) dimming control technique. Thisapproach allows display brightness tofluctuate fully as needed in response toambient light, providing bright daylightdisplays and a comfortable low-levelnighttime mode. Night mode brightnesslevels are typically less than one per-cent of the maximum daytime levels(see Figure 1).
This second approach yields a muchhigher viewer satisfaction solution thatrapidly is establishing itself as the lead-ing technology for automotive displays.It provides true, flicker-free uniformlamp-dimming across the extremerange of ambient light and harsh tem-perature conditions experienced inevery vehicle. Importantly, it also is per-fectly suited for every current andplanned automotive display applicationincluding still data, GPS graphics, full-motion “blind spot” and traffic avoidancemonitoring, and rear passenger enter-tainment video displays.
In addition, integrated circuit controlrequires much lower power levels whenoperating in low brightness, than withthe “screen reversal” technique. Thisprovides additional advantages in termsof lamp life, cluster heat and reliability.Since all of this can be achieved with nocost penalty, it has become the pre-ferred system-level design choice fortoday’s sophisticated automotive infor-mation and entertainment displays.
Automotive Performance RequirementsCCFLs are the preferred choice for
automotive display applications becauseof their superior brightness capability ascompared to the alternative of light emit-ting diodes (LEDs), which can be usedin less demanding handheld displayapplications such as mobile phones and PDAs.
Figure1. Integrated circuit-based backlighting control technology enables brightness levels to automatically adapt to changing automotive ambient environments. In this example, an LX1800 integrated circuit has been added for additional digital microprocessor control.
Figure 2. Automotive display systems require high performance at low temperature.
So how do we emulate eye-like per-formance in automatic display control?The answer is superior sensor technolo-gy. Because earlier sensors wereextremely susceptible to infrared andultraviolet light, they often provided falsereadings based upon these non-visiblelight sources. Often the results wereunpredictable, resulting in brightnessadjustments contrary to the desired lev-els. Display brightness adjustmentsmight be triggered by unseen infrared orultraviolet light originating from suchsources as the sun, incandescent lightbulbs, fluorescent lamps and even heat.Poorly designed systems would set upan erroneous display brightness basedon high UV and IR content.
In contrast, today’s latest sensorshave the ability to detect and respond tolight wavelengths that correlate veryclosely to the response characteristicsof the human eye itself. These sensorseliminate several problems encounteredwith prior technology. Figure 3 shows anexample of the latest sensor technolo-gy’s response profiles as compared tothose of the human eye.
In addition to delivering improvedspectral response, these new siliconsensors such as the Microsemi LX1972(Fig. 1) also offer extremely good tem-perature stability. This is essential asmost CCFLs or LED backlit displaysexperience substantial temperatureswings as they operate, especially in anautomotive environment. Poor tempera-ture stability can result in erroneouschanges to display brightness based ontemperature and not light. A light sensorshould not be a “thermostat.”
Automotive Displays of the FutureTechnology is on its way that will
extend flicker-free operation well beyondtoday’s 225:1 display brightness levelsto as much as 300:1 levels and beyond,and at lower costs. This will be achievedover the full automotive temperaturerange with solid fault detection.
We also will be able to achieve acce-ptable levels of electromagnetic interfer-ence (EMI) and interference for “head unit”environments, and we will see the broadadoption of “human eye” light sensortechnology that will enable automaticadjustments to display brightness.
Despite the many stringent technicalrequirements and a demanding costmodel associated with advanced flat-panel automotive display systems, luxury car manufacturers continue tolead the way in implementing them.Meanwhile, consumer enthusiasmgrows for vehicle video applications that also require the brightness of LCD screens.
As these differentiating featuresprogress globally downward into mid-level vehicles and below, an increasingnumber of consumers will benefit fromthe many advancements in lamp con-struction, system engineering, andbacklight power-management designsbeing pioneered for displays found inthese luxury brands.
System-level performance expecta-tions continue to grow. With ever more
demanding applications for safety andentertainment, automotive displays willfavor the bright CCFL backlighting foundin LCD designs—even as organic light-emitting diode (OLED) and LED tech-nologies seek to find ways to competewith these current solutions.
Meanwhile, wide-range backlightingdimming technology under integratedcircuit control continues to solidify itsposition as the ideal solution for meetingthe rigorous automotive display require-ments found in both current and futuredesigns. Its performance is onlyenhanced by the incorporation of the latest “human eye” light sensors forautomatic brightness control.
22 Power Systems Design Europe March 2006 www.powersystemsdesign.com 23
COVER STORY
www.microsemi.com
To operate in bright sunlit ambientenvironments, automotive display back-lighting systems may be required to provide outputs in excess of 600 cande-las/m2 (nits). This is approximately four times the brightness provided in atypical laptop computer (see Figure 2).Current LED offerings used in PDAsand other display products of similarsize provide light output an order ofmagnitude below what is needed tomeet dashboard readability require-ments in full daylight conditions.Continuing LED development is under-way with the goal of meeting these higher light output goals.
Nighttime driving conditions requireperformance at the opposite end of thebrightness scale as well. In these condi-tions, flicker-free backlight operationmust be capable even down to the 1 to 2 nit range. Traditional analog lampcurrent control cannot achieve theselevels. To provide a consistent, safevisual environment for both driver andpassengers, CCFL automotive displaysmust be able to handle dynamic dim-ming ranges of greater than 250:1. This is more than 10 times those typically provided in the very best computer displays.
Dimming at these low light levels cre-ates additional challenges, even for theadvanced duty cycle drive techniquesemployed in today’s pulse-width-modu-lated (PWM)-driven inverters. For exam-ple, at the low duty cycles encounteredwhen providing light levels below onepercent of rated maximum, only a fewlamp current bursts per cycle, are firingthe CCFLs each cycle. Here, any varia-tion in the number of PWM pulses perburst would appear as unacceptable display characteristics. All of these challenges, however, can be met whenusing the proper system engineeringapproach.
Thermal IssuesUnlike most consumer goods, auto-
mobiles must operate in temperatureextremes from -40 to +85 °C, furthercomplicating display ballast design.CCFLs must provide the same high out-puts for optimum readability on winter
mornings in cold climates as they do onafternoons in the tropics. Failure to doso can lead a driver to believe that thedisplay is not functioning. As a result,various forms of high pressure (alsoreferred to as self-heating) lamps havebecome the standard for cold weatheroperation of automotive displays.
Self-heating lamps can require strikevoltages as high as 3,000 volts, orabout four times the strike voltage ofCCFLs used in comparably-sized stan-dard displays. In addition to these highvoltage requirements, boost (currentoverdrive) techniques are employed toachieve driver-suitable brightness levelsquickly when displays are turned on incold weather. Lamp current overdrive ofas much as 50 percent may be used toachieve this rapid “warm up.”
This combination of voltage and boostpower requirements needs to be man-aged carefully at the system level froma software and hardware standpoint. Agood portion of that effort is applied tothe transformers. Consequently, highvoltage transformers used in conven-tional inverter designs require significantre-engineering to operate in automotiveapplications. As the final challenges, allof these advanced performance capabil-ities must be done while meeting thenecessary target costs and form factors.
Fault ProtectionBulb fault protection is particularly crit-
ical in automotive backlighting systems,since any arcing or unwanted strikingdue to a missing, or accidentally-dam-aged, CCFL lamp is simply not allow-able in the possible presence of vapor-ized or liquid gasoline.
In automotive inverter topologies, thesensing of bulb current provides faultdetection—a lack of current denotes anopen circuit and a failed or damagedCCFL lamp. At low brightness levelsand low duty cycles, differentiating lampcurrent from parasitic leakage and sys-tem noise can be difficult. But clever circuit design has been demonstrated tomeet this challenge in a number of auto-motive display products.
Human “Eye-Like” SensorPerformance
Of course, any discussion of automat-ic brightness control implementationmust include an analysis of whether thedesired automatic control can be met atthe necessary cost targets. Fortunately,this cost/performance design challengeis now being met by a new generationof optical sensors capable of providinghigh-performance automatic brightnesscontrol at low cost.
When it comes to controlling displaybrightness in response to fluctuatingambient light conditions, the best tem-plate is the human eye, a high perform-ance standard, especially for automo-tive displays. The human eye constantlyadapts to different light conditions, auto-matically and easily. Thus emulating thespectral response of the human eyebecomes critical for any effective displaybrightness control technology.
The second requirement is to elimi-nate human involvement. Brightnessadjustments must be automatic. Studieshave shown, for instance, that mostconsumers of handheld cell phones andPDAs can’t recall how to change thebrightness level manually. And, evenwhen they do know, consumers say thatchanging display brightness takes moretime or trouble than is warranted forsuch simple viewing needs as retrievingan appointment or phone number, ordialing a phone number. Even laptopcomputer users rarely bother to lowerbrightness levels, even though theyknow it would extend their battery oper-ation. It is obvious that the only way togain the many benefits achieved withvariable display brightness is to auto-mate the adjustment process. Simplyremove that responsibility from the user.
There is even less chance that driverswill adjust display brightness manually.An automobile moving in traffic does not lend itself for any added distrac-tions. Additionally, the impact of failingto change display brightness is oftenmoderated by the excellent design ofthe human eye itself—as it continuallyadjusts its aperture to block orreceive light.
COVER STORY
Figure 3. Sensor response is approaching human-eye capabilities, a critical factorfor controlling display brightness characteristics.
24 Power Systems Design Europe March 2006
Technologists pushing the performance of exciting new technology
All electrical and electronic equipment uses some form of power management, from a simple on-off switch to the sophisticated power management unit (PMU) in a
third-generation cellular handset.
By Paul Greenland, Strategic Marketing Director, Power Management Group, and Werner Berns,Power Application Design Center Manager Europe, National Semiconductor
Technologists pushing the perform-ance envelope for tomorrow’smicroprocessors reluctantly admit
that getting the power into the chip andthe heat out are major challenges, con-current processing techniques notwith-standing. Power management hasreached the status of a true enablingtechnology. This article examinesemerging applications, impending legis-lation and standards, as well as excitingnew technology that will enhance theperformance and functionality of tomor-row’s equipment.
LED lightingHigh-brightness white LEDs or mixed
red, green and blue light from LEDs, israpidly spreading out in environmentswhere high luminous efficiency, shockresistance and small size are an advan-tage. In automotive applications for sig-naling and illumination, LED lighting hasan impact on safety and the ergonomicsof the vehicle. A short trip through thestreets of European cities will revealLEDs in the majority of traffic signalswhere their extended life makes the traf-fic light almost maintenance-free. LEDbacklighting in flat-panel displaysenhances the color, depth perceptionand intensity of the image while simulta-
neously reducing power consumption.High-brightness LEDs are driven with aconstant current, and high-power LEDscan draw up to an Ampere. Where multi-ple strings of LEDs are used, care mustbe taken to ensure that the current ineach string is matched to that flowing inall the other strings in an array.
The junction temperature of the LEDaffects the color temperature or spectralfrequency of the light emitted and it’sluminosity. Where red, green and bluelight is mixed to form white for a display,compensation for these effects is essen-
tial. LEDs are also attractive where cool-er, concentrated light sources are used,such as in endoscopes for laparoscopicsurgery and for the spot curing of dentalcomposites. In cellular handsets, LEDsare used since many years and it’susage is not limited to the LCD back-light, but also used as “fun-light”.
Digital management & controlAs the number of complex loads in
distributed power architectures andhigh-end consumer applicationsincreases, so does the requirement for sophisticated power management.Complex loads such as DSPs, FPGAsand microcontrollers frequently havemore than one supply rail. The centralcore or data-processing brain of thedevice runs from an ever-decreasingvoltage driven by Moore’s law. Theinput-output circuit or communicationinterface runs from a standard higher-voltage rail. As the core supply potentialdrops below a volt, leakage currentsflowing in the devices therein increase.Substrate biasing schemes that apply a negative voltage offset to reduce thisleakage current are common in state-of-the-art graphics and digital signalprocessors. Some attention must bepaid to the sequencing and control of
Figure 1. LEDs makes the traffic lightalmost maintenance-free.
www.powersystemsdesign.com 25
POWER MANAGEMENT
26 Power Systems Design Europe March 2006
different rails for reliable operation. Thistype of control is referred to as “digitalpower management” or “digitally assist-ed power management.”
Digital power control, sometimescalled “processor inside the loop” is anentirely different matter. Digital powercontrol entails comparing two digitalwords to produce a pulse width drivingthe power switch, rather than using thetraditional analog PWM comparatorapproach. This adaptive technique iscompelling in applications where thetime constants of the load allow powerstage operation below 100 kHz, forinstance power factor correction, unin-terruptible power supplies, multi-chem-istry battery charging and motor control.The other application is in PMUs for cel-lular handsets and PDAs where severalfully synthesizable PWM cores aredeployed, together with control, diag-nostic and interface circuitry. Run-timecontrol schemes, where the sub-circuitor peripheral is supplied with the opti-mum operating voltage for its currentstate of operation to save energy, bene-fit from digital power control whichmakes the regulator more agile andresponsive.
Legislation & StandardsRoHS
Legislation and standards havealways driven power management
technology. In recent years, Europeanlegislation for power factor correction,electromagnetic compatibility and world-wide energy-saving initiatives havespawned innovative power managementtechniques. The latest Restriction ofHazardous Substances (RoHS) meas-ures are causing customers to switch tolead-free semiconductor packages andinvestigate alternatives to cold cathodefluorescent lighting which containsminute amounts of mercury.
EMCAs the electromagnetic spectrum
becomes more crowded, it becomesunavoidable that compatibility standardswill be made more stringent. This willstimulate new power managementtopologies and control developments.Spread-spectrum or dithered clock tech-niques, which integrate the peaks in theelectromagnetic spectrum generated byswitching power supplies, are well-known. Soft switching and resonant con-verter technology, where the switchingtransition is a portion of the sine wavewith low high-frequency harmonic con-tent, will experience a renaissance innoise-sensitive applications.
Energy EfficiencyLimited natural resources and fast-
growing energy-hungry economies pushup fuel costs and motivate investigationof alternative energy sources. Advisory
standards on energy efficiency will soonbecome mandates, eliminating ineffi-cient appliances and office equipment.The power supply designer is the stew-ard of energy in electrical and electronicequipment. Measures to increase ener-gy efficiency include multimode opera-tion (standby and sleep mode), run-timeand sweet-spot control, where devicesare supplied with the optimum voltagefor peak efficiency and precise matchingof switch to load and driver to switch.White goods that communicate throughthe Internet with the utilities, drawingpower which smoothes out fluctuatingdemand have been proposed. Studieshave shown that replacing all motordrives in industrial applications with effi-cient vector-controlled drives wouldresult in North America not having tobuild power stations for the foreseeablefuture.
Technology: Copper Escalating power density and efficien-
cy requirements motivates investigationof techniques to increase the currentdensity of integrated regulators. Oneweapon in the arsenal available to thepower management IC designer is theuse of a copper current redistributionlayer. Copper has a higher thermal andelectrical conductivity than the aluminumused for integrated circuit interconnec-tions and power switch electrodes. Thistechnology, coupled with multi-chip tech-niques that allow the designer to com-bine sophisticated digital control, preci-sion analog and high-current densitypower devices in the same package,holds great promise.
Integrated PassivesAny study of increased power density
would be incomplete without the investi-gation of components that store energy.Considerable research has been con-ducted on the integration of passivecomponents into semiconductor packag-ing and combination devices such as the integrated L-C-T (Inductor-Capacitor-Transformer). Integrating thefilter inductor into semiconductor pack-aging makes a lot of sense, particularlyfor non-isolated point-of-load regulators.Co-packaging the inductor with the reg-ulator chip reduces parasitic resistancesand radiated emissions. Also, it is one
Figure 2. Advanced Power Management.
www.powersystemsdesign.com
step toward making the switching regu-lator as easy-to-use as a three-terminalregulator. Wound component designhas always been a black art to the sys-tem designer, rivaled only by the mys-teries of loop compensation.
Silicon CarbideSemiconductor technology experts
are continually pushing the boundariesof power device capability. SiliconCarbide has some of the most attractiveproperties of any semiconductor yetdeveloped. It withstands voltages eighttimes higher than silicon; it conductscurrent up to 100 times more freely; and it conducts heat better than gold.Random thermal fluctuations createelectron-hole pairs causing leakage current and electrical noise in all semi-conductors; this effect is 16 orders ofmagnitude lower in SiC. The SiC powerswitches now coming onto the marketcan operate 10 times more efficientlythan their silicon counterparts. Thistranslates to a 10-fold increase inswitching speed, or a to-fold reduction in die area for the same power rating.Silicon Carbide also has been used forjewelry, super-abrasive coatings formachine tools, and to line the brakes ofthe Porsche 911 turbo, reducing rotorweight by 16kg, increasing friction by 25%and lifetime to more than 300,000 km.
Power management is a far moredynamic and compelling discipline nowthat it is acknowledged that effectivepower management enables new tech-nology and differentiates the perform-ance of end-equipment. Legislation andstandards continue to stimulate anddrive research and innovation. The environmentally conscious power supplydesigner is a key contributor to the ener-gy efficiency and electromagnetic com-patibility of equipment. Traditionally,power supply design was “afterthoughtengineering,” considered only after asystem design was complete.Nowadays, power considerations areincreasingly part of the concept stage ofdevelopment, and justifiably so. NationalSemiconductor is providing state-of-the-art power management solutions to theircustomers. With the recently openedPower Application design center inNational’s European Headquarters inFürstenfeldbruck, Germany, it goesbeyond the point of “just” providingpower management IC’s. The newdesign center can provide customizedreference designs and proposals fortomorrow’s power design needs.
Figure 3. LM1770 easy-to-use three-terminal regulator.
www.power.national.com
POWER MANAGEMENT
www.powersystemsdesign.com 2928
Fine tuning by capacitor valueA step-down converter can be optimized for small space and fast transient response. An example
is given, based on the TPS6420X step-down controller.
By Thomas Schaeffner, Texas Instruments
Step-down converters for batteryoperated equipment need to fulfill certain requirements:
• Small board area for the total application
• Easy to use• High efficiency meaning• Optimized for low input voltage• Low quiescent current
The area used for an application canbe minimized by using external compo-nents in packages with small footprintsas well as by minimizing total part count.
As compared to a converter with inte-grated switches, a controller has exter-nal switches in addition to supportingpassive components. Therefore, thecontroller’s control topology, as well asits input voltage range and quiescentcurrent, must be considered early duringdevelopment of the controller IC in orderto ensure minimal external part count forthe final application. There are differentcontrol methods that could be used forsuch a design:
• Pulsewidth modulation (PWM)• A combination of pulsewidth modula-
tion and pulse frequency modulation(PWM/PFM)
• Hysteretic• Fixed-On-time or fixed-OFF-time
Operating Principle:The TPS6420X is a controller for non
synchronous step-down convertersoperating with a minimum on-time/mini-mum off-time control scheme. An exter-nal PMOS transistor is switched on untilthe output voltage has reached thenominal value or the current limit hasbeen exceeded. Once turned off, thePMOS stays off for the minimum off-time and is only turned on again whenthe output voltage has fallen below itsnominal value.
In figure 1, a typical application isshown. The ripple current is set by theinductor value, by the switching frequen-cy as well as by input and output volt-age. The value of the output capacitorsets the ripple voltage in steady stateoperation as well as voltage drop duringload transients.
Typically, a small capacitor in parallelto R1 is recommended to reduce theeffect of parasitic capacitance from thefeedback pin to ground. In order to get agood overdrive for the internal compara-tor, the parasitic series resistance in theoutput capacitor (ESR) should be in therange from 30mR to 150mR.
Table 1. Pros and cons for converter methods.
POWER CONVERSION
Power Systems Design Europe March 2006
www.powersystemsdesign.com 3130 Power Systems Design Europe March 2006
The application according to figure 1can be further optimized with regard tosmall solution size by:
• Increasing the switching frequencyand use of a small inductor value
• Replacing the tantalum with aceramic capacitor
The switching frequency for a given
input voltage range and output voltageis set by the minimum on-time or mini-mum off-time of the controller. It is there-fore important to select the optimumdevice for the application. There are fourdifferent versions—TPS64200 toTPS64203 available. The only differ-ence is the minimum on-time and mini-
mum off-time. The table „selecting theright device for the application“, given inthe data sheet helps to select the rightdevice without the need for complicatedcalculations.
More details are given in an applica-tion report (SLVA160) about TPS64200.Another helpful tool is a Microsoft-EXCELbased spreadsheet (SLVC038.ZIP),which can be downloaded from the TIwebsite. It can be used to determine thevalue of all external components as wellas basic operating parameters likeinductor current ripple and switching fre-quency. By replacing TPS64200 withTPS64203, the switching frequency inour application will be increased and theinductor value can be reduced to 4.7uH.
Ceramic capacitors with a capacity of47uF or lower are not only smaller insize compared to tantalums, they arealso a more ideal capacitor with almostno series resistance (ESR).
Figure 1. 1.8V-Step-down converter with 47uF Tantalum output capacitor.
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www.powersystemsdesign.com 3332 Power Systems Design Europe March 2006
The output capacitor has beenincreased and the feed forward capacitorCff has been increased to accommo-date the larger output capacitor. Theoutput voltage almost shows no tran-sient voltage overshoot and undershoot.
The optimal value of the feedforwardcapacitor Cff can easily be determinedby measuring the transient response.With a too small value, the control loopdelay is too high and the voltage willshow large over- / undershoot. With a
too large value, there will be a voltageovershoot when the load is removed.Figures 3 to 4 show the behavior at different conditions.
ESR of Tantalum is 30mR to 150mwhile Ceramic X5R or X7R is typically5mR. Therefore, the output voltage rip-ple caused by ESR is smaller by a fac-tor of 6 to 30 for a ceramic capacitorcompared to a tantalum. While a smallvoltage ripple is ideal from an applica-tion point of view, the comparator insideTPS6420X needs a certain voltageoverdrive at its input for proper opera-tion. ESR of a tantalum capacitor pro-duces an almost linear voltage rise inthe output capacitor as inductor currentrises. However, the voltage rise causedby the much smaller ESR of the ceramiccapacitor lags behind the rising inductorcurrent, causing a lower switching fre-quency and a sinusoidal voltage at theoutput. To replace the tantalum capaci-tor with a ceramic capacitor, one addi-tional passive component, R1b asshown in figure 2, is required.
The upper resistor of the output volt-age divider is split into two segments.R1a monitors the output voltage directlyat the output capacitor while R1b con-nects to the switch node, the nodebetween the power transistor and theinductor. Since the average voltageacross an inductor equals zero, the volt-age sensed by R1b at the switch nodeis equal to the output voltage excludingthe voltage drop caused by the resist-ance of the inductor. If R1b was the onlyfeedback resistor in the system, theaverage output current times the resist-ance of the inductor would cause theoutput voltage to drop with the outputcurrent. Therefore, R1a is used toreduce this effect.
Using both R1a and R1b in parallel will:• Slightly decrease the output voltage
with load current• Couple an AC voltage to the FB-pin
The ratio of R1a and R1b determinesby how much the output voltagechanges with current for a given induc-tor. A ratio of R1b = 2 …4 x R1a is suffi-cient. If the resistance R1b is too lowcompared to R1a, the output showshigh output voltage change with current,but is usually easier to stabilize by Cff.
Additional advantages:• Low output voltage ripple
• Small output capacitor (size andcapacity)
• Fast transient response• Load dependent dc output voltage
gives additional margin during loadtransient
Equation 1 provides a good startingpoint for the value of Cff, given the feedback resistors, average input voltage and predicted switching fre-quency per the software tool slvc038.zipfor the TPS6420x which is available at www.ti.com.
Where fsw is the switching frequencypredicted by the design tool, assuming ahigher ESR capacitor is being used, andVREF is the reference voltage of thecontroller IC (1.213 V for the TPS6420x.During bench testing, Cff may need tobe increased or decreased slightly tofind the value that gives optimal loadtransient performance and acceptableoutput ripple at light load.
The following scope plots show tran-sient response. As already mentioned,the output voltage drops slightly with theload current. This however is an advan-tage for transient response. The energystored in an inductor is proportional tothe square of the load current (E=1/2LxI2).The higher the load current, the higherthe energy stored in the inductor. When
the load is abruptly removed , this ener-gy will be delivered to the output andcharges the output capacitor. Even if thecontrol loop could react with no timedelay, the output voltage would rise for a short period of time. The transient voltage rise can only be reduced by:
• Larger output capacitance• Smaller inductor value
Since the output voltage at high out-put current is slightly less than the nomi-nal value, it is easier to design the appli-cation in such a way to keep the voltagewithin tolerance during a load transient.The dependency of the output voltage ofthe load is also an advantage when theload current increases quickly. Evenwith a small inductor value, the inductorcurrent needs time to rise to the highervalue. During this time, the energy hasto be delivered by the output capacitor,causing the output voltage to drop evenif there is no delay in the control loop. Thecircuit can be designed in such a way thatthe output voltage at no load is slightlyabove the nominal value, making it easi-er to stay within the limits for the outputvoltage also for a positive load step.
High voltage over- / undershoot dur-ing load transient caused by a too smallfeedforward capacitor. The PMOS doesnot turn on/off continuously during theload step.
Figure 2. 1.8V-Step-down converter with 22uF ceramic output capacitor.
Equation 1. Starting point for the value of Cff.
Figure 3. Feedforward capacitor too small. Vin=3.8V,Vout=1.8V, Iout=80mA .. 720mA .. 80mA, Cff=33pF,Cout=22uF. Channel 1: output voltage, Channel 4:inductor current.
Figure 4. Larger output capacitor and larger feedforwardcapacitor. Vin=3.8V, Vout=1.8V, Iout=80mA .. 720mA ..80mA, Cff=220pF, Cout=2 x 22uF. Channel1: output volt-age, Channel 4: inductor current.
www.ti.com
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www.powersystemsdesign.com 3534 Power Systems Design Europe March 2006
The general availability of USB ports on todays computers make them an attractive option forpowering or charging devices, though this has its pitfalls.
Guido Körber, Code Mercenaries
Negotiation with the system for optimum power supply
Drawing power off the USB is notas simple as it might seem at firstglance. A USB port does supply
5V to a connected device as long as thecomputer is powered. But the availablecurrent can vary over several orders ofmagnitude. Before grabbing a USB plugand connecting the power supply lines tosome device it is a good idea to under-stand how power is managed on the USB.
USB does have a power managementscheme that can be followed only by areal USB device that understands thebus protocol. Just connecting to thepower supply lines of the USB can resultin drawing more current than allowedwhich can cause other devices connect-ed to the bus to fail because the supplyvoltage drops, or it can drain the batteryof a portable computer.
There are two options for the powersupply of USB devices. A device can be “self powered” in which case it doesnot draw power off the bus and has tohave its own power supply, or it can be“bus powered”.
When a USB device is plugged into aport it may draw up to 100mA until itgets configured by the host or until itdetects the bus to be suspended (i.e.computer went to sleep mode). In caseof a suspended bus the device has toreduce its current to just 500 μA or insome configurations to 2.5mA.
Depending on the port it is connected toa device may draw up to 100mA or up to
500mA once it is configured by the hostcomputer. Ports on a computer or on a“self powered hub” allow 500mA perdevice. Ports on a “bus powered hub”like the ones in a keyboard allow only100mA for each device. But since thedevice can not tell which kind of port itgets connected to it has to constrain itscurrent to 100mA until it gets configuredto use more, or it even has to drop to500μA if it detects that the host comput-er is sleeping.
USB hubs and ports have overcurrentprotection that prevents damage result-ing from a misbehaving device. But theprotection usually has a relatively widemargin to prevent tripping on inrush cur-rents when a device gets plugged in.Typically a bus powered hub which cansupply 100mA on each of its maximum4 ports will not have its protection kick inbefore almost 1A is drawn combined onall its ports. Long before that the over-current will result in a voltage drop thatcan affect other devices and destabilizethe whole USB setup.
Devices like portable media players donot have a problem following the powermanagement of the USB since theyhave a USB controller in any case. Butfor simple devices the development of thenecessary controller can be quite costly.
Depends on the OSBy using so called descriptors a USBdevice advertises its capabilities andrequirements to the system. USBdevices have the option to offer a num-
ber of alternate configurations for differ-ent operating modes. One of the proper-ties defined for each configuration is thecurrent required by the device whenused in that specific configuration. If adevice does actually get configured forthe maximum current available dependsto a good part on the operating system.
The current implementation of USB onLinux does the worst job. It just grabsthe first configuration and enables itwithout checking if there is sufficient current available. So using bus powereddevices with Linux depends on the userto keep track.
Windows in its various versions does aslightly better job. It looks at the firstconfiguration and enables it if there issufficient current. If there is not sufficientcurrent the device will not get enabled,no checking for alternate configurationsis done.
Only MacOS X checks the available con-figurations until it finds one for which ithas sufficient current and enables this one.
A power controller should know about allthese details and make the best effort toget the maximum current allocated. Sinceit is not possible for the device to detectwhich operating system is running onthe host computer it has to use a trialand error approach in case of Windows.For Linux it is currently not possible todo automatic power optimization untilthe USB function gets fixed.
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www.powersystemsdesign.com 37
Layout, component selection anddebugging of the power supplyconsume more time and require
extensive power supply design expert-ise. A digital designer’s time is betterspent interfacing sophisticated digitalICs and writing code than analyzing the load transient response of a DC/DC circuit and defining the inductor,MOSFETs and capacitors. Let’s not for-get the output current ripple and loopstability calculations.
Pre-manufactured DC/DC power sup-plies, also referred to as point-of-loadmodules, have been promising simpler,smaller and quicker solutions but theyfall short in meeting the demands forsystem assembly of densely populatedembedded boards. Some power supply
solutions require an external inductor,many additional input and output capac-itors, and compensation circuitry. Mostare assembled on a small printed circuitboard (PCB) and require hand inspectionfor reliability, since the circuit componentsare exposed and not encapsulated.
For heat dissipation and safe compo-nent spacing, many embedded systemsspecify a maximum thickness for boththe top and bottom of the board.Unfortunately, high power densityDC/DC modules must implement tallinductors and rely on thick PCBs to alleviate heat dissipation. The large size and tall profile inhibits their use.Therefore, a designer must eitherdesign a discrete power supply where it can be optimized to meet the profile
requirement or rely on lower powerDC/DC modules where thinner inductors are used.
System designers are compelled tomake compromises in the selection,performance and definition of the opti-mum power supply. The best solution isa complete power supply with no exter-nal power components, no mathemati-cal analysis, easy layout and a productthat fully meets the surface mountassembly requirements, just as theother digital ICs on the board. The result is a solution that is easy to select,design and assemble.
Complete Power Supply in an ICForm-Factor
Figure 1 shows a complete DC/DCpower supply solution. This IC-like solu-tion is a 10A synchronous switchmoderegulator with built-in inductor, support-ing power components and compensa-tion circuitry (see Figure 2). TheLTM4600 is the DC/DC module thatmeets the spacing and assemblyrequirements of the densely populatedand advanced embedded systems. Thisencapsulated μModule DC/DC powersupply is housed in a 15mm x 15mm x2.8mm LGA package. Its size is smallerthan most FPGAs and processors. Withonly a 2.8mm profile, the LTM4600 can
Defining and designing a DC/DC power supply is often the final design step for digital systemdesigners. Designers must spend precious time on the design, layout and debugging of a
DC/DC regulator circuit. Identifying an appropriate DC/DC controller IC, MOSFETs, inductor, capacitors, resistors and diodes are just part of the challenge.
By Afshin Odabaee, Product Marketing Engineer, Power Management Products,Linear Technology Corp.
A power supply at the size of an IC
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36 Power Systems Design Europe March 2006
What the Vampire does for youThe IOW24PowerVampire does thenegotiation with the system for optimumpower supply. Building a device thatneeds USB basically as a power sourceis getting very simple with IOW24PV.Besides signaling the available powerIOW24PV also offers 12 generic I/Olines that can be accessed from applica-tions running on the host computer.Some of the I/O pins can be used for aIIC and/or SPI Master port to connectadditional circuitry.
IOW24PV provides a status line eachfor the availability of power and thepower level. To simplify external circuits
it has both signal lines in inverted andnot inverted form. It also has an inputthat restricts it to negotiate only for 500mAin case a circuit can not operate at allwith 100mA.
When combined with the LTC3455 chipby Linear Technology (see PowerSystems Design Europe Nov. 2005) you get a complete power managementsystem including a LiIon charger. TheNational Semiconductor LP3947 offerssimilar features as the LTC3455 but italso has an IIC interface to set chargingparamters which can be done via the IICfunction of IOW24PV.
Lighting upA simple design example is a LED lightthat selects its brightness depending onthe available current. Cascading twohigh side power switches like the MicrelMIC2025 and controlling them byIOW24PV allows to build a USB stan-dard compliant LED light. Depending onhow much current is available eitheronly one or all six of the LEDs light up.With a forward current of 70mA perLED, a worst case current of 20mA forIOW24PV, and a few μA for the switch-es this circuit always stays within the100mA or 500mA current budget.
Taking controlThe I/O functions of IOW24PV can becontrolled by an application running onthe host computer. No driver installationis required, IOW24PV uses standardsystem drivers. Since it is part of the IO-Warrior chip family of Code Mercenariesthere are libraries and sample code forLinux, MacOS, and Windows available.The programming support includes Javaand AppleScript.
Figure 1. The IOW24PV needs only minimalexternal components and allows glueless inte-gration with power management chips like theLTC3455.
Figure 2. Adding two high side switches like MIC2025 allows a deviceto adapt to the available current. Like this simple LED light which usesSuperflux LEDs with a typ. forward current of 70mA each.
Figure 3. The LED lamp built on a IO-Warrior starterkit. This one is plugged into a high power port, all LEDs are on.
www.codemercs.com
Figure 1. The LTM4600 is a complete 10A switchmode DC/DC power supply withlayout and assembly as simple as an IC.
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www.powersystemsdesign.com 3938 Power Systems Design Europe March 2006
not decided to convert to lead-free man-ufacturing and where the LTM4600 canbe qualified immediately for surfacemounting with Pb-based pastes. In addi-tion, lead-free exempt manufacturerssuch as military and some industrialcompanies can take advantage of theLTM4600’s benefits, although theμModule is RoHS compliant. A copy of the LTM4600 RoHS material declaration is available atwww.linear.com/micromodule
Only 1.73 GramsBeside its tiny and low profile size, the
LTM4600 weighs only 1.73g. This highvoltage and high power supply requiresno special surface mount tooling proce-dures or machines. The μModules lightweight and small size is easily handledby the same pick-and-place machinesas the ones used with FPGAs andmicrocontrollers. This compatibilityspeeds manufacturing of high densitysystem boards such as AdvancedTCAor CompactPCI.
The LTM4600 DC/DC μModule repre-sents a new architecture for point-of-load power supplies, significantly simpli-fying the power design task. InnovativeDC/DC design and improved packagingtechnology allows a digital systemdesigner with minimal analog knowl-edge to quickly construct a high per-formance DC/DC power supply.
In addition to ease of design, the layout and assembly are simple andstraightforward. The LTM4600 uses thesame pick-and-place machines as thedigital ICs on the board. Although thisμModule is capable of delivering highoutput power, its excellent thermal char-acteristics allow it to be placed near theother ICs. The LTM4600’s small sizeand low profile design mean that digitalsystem designers no longer must sacri-fice expensive board space or compro-mise on the performance of point-of-load power supplies.
www.linear.com
be readily placed on the backside of a board.
This μModule is rated for 20V and28V input operation (two versions). Theoutput voltage is adjustable with a singleresistor from 0.6V to 5V. The LTM4600can deliver up to 10A of output currentand offers excellent transient responseto fast changing load current transients.
Easy Design Replication by Copyingand Pasting the Layout
A common complaint among systemdesigners is the assembly-house’s alter-ation of a specified layout. The result ismany rounds of debugging layouts. Thisproblem is alleviated with the LTM4600.The simplicity of the LTM4600 minimizeslayout errors. The μModule’s assemblyrequires no special tooling. This simpleassembly and layout allows twoLTM4600 μModules to share the load,therefore doubling the output currentcapability for higher power applications.
Excellent Thermal PerformanceThe LTM4600 μModule has only
15ºC/W thermal resistance. It avoidsoverheating by dissipating heat efficient-
ly from both the top and bottom of thepackage. The device’s packaging tech-nology permits delivery of 10A load cur-rent at 3.3V from a 12V input with excel-lent thermal performance. For applica-tions with high ambient temperature, the LTM4600 with a heatsink and someair flow still exhibits exceptionally goodthermal performance even at highpower. A detailed application analysiswith thermal imaging photos under varietyof conditions is provided atwww.linear.com/micromodule
High Input Voltage, Ultra-FastTransient Response
The LTM4600, unlike other DC/DCpoint-of-load modules that have limitedinput range, can convert input supplyvoltages as high as 28V, without anyinput supply protection or additionalexternal components. The output voltageis adjustable from 0.6V to 5V with ±1.5% accuracy.
A unique capability of the LTM4600 isits no-clock latency current mode archi-tecture, allowing it to respond quickly torapid load current changes. Where othermodules must wait one full clock cycleto pass before responding to a load
change, the LTM4600’s response is instant,eliminating up to five external loadcapacitors required with other solutions.
20A Load Current by Paralleling Two μModules
Two LTM4600 μModules can be easilyparalleled to provide more than 10A (upto 20A) output current. The μModulefeatures a current mode control schemewhich ensures excellent current sharingamong the devices. Sharing the loadcurrent among two μModules and bal-ancing the power dissipation minimizesthe thermal stress and reduces require-ments for heatsinking and airflow.
By interconnecting only three pinsbetween two LTM4600s, a power supplycan be easily scaled for higher outputcurrent. All the necessary circuitry forbalanced and accurate current sharingis integrated. There are no requirementsfor external op amps and supportingcomponents. Refer to the LTM4600 datasheet for details and schematics of a20A solution at 2.5V from a 4.5V to 20Vinput supply.
RoHS Compliant; Mounts with bothPb-based and Lead-free Solder Pastes
The LTM4600 is RoHS compliant.However, unlike many lead-free packageswith matte-tin lead finish, the LTM4600is offered with gold-finish pads. Gold-fin-ish pads allow the μModule it to be usedwith either PbSn- or SnAgCu-based sol-der pastes for surface-mount processing(Figure 3). This unique feature is espe-cially attractive to companies that have
Figure 2. The LTM4600 requires minimum external components. The difficultcompensation circuitry, inductor, MOSFET, DC/DC controller and input/outputcapacitors are on-board. 1.5V, 10A application is shown here.
Figure 3. Gold-finish pads allow theRoHS compliant LTM4600 to bemounted with Pb-based and lead-freesolder pastes.
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www.powersystemsdesign.com 4140 Power Systems Design Europe March 2006
Power a human body area networkMiniaturized and cost-effective thermoelectric generators (TEGs) scavenging energy from wasted
human body heat are good candidates to power the human body area networks of tomorrow.
By Mieke Van Bavel, IMEC, Leuven
Such a network could be com-posed of electronic modules withwireless sensors and actuators
that typically consume 100μW of powerper sensor node. This power is obtain-able on several square centimeters ofthe skin, i.e., the typical size of a minia-ture electronic module.
In order to model and design efficientsmall-sized TEGs, IMEC has measuredthe thermal properties of the humanbody that is used as a heat source.Based on the results of this investiga-tion, prototypes of the TEG have beendesigned and tested. Watch-sized proto-types made of miniaturized commercialBiTe thermopiles have demonstrated togenerate sufficient output voltage andpower to supply the wireless sensormodules. Research on next-generationTEGs using the less expensive micro-machined SiGe thermopiles is currentlyongoing. They could possibly replacethe batteries in a consumer product,operating on a human body, with small-size scavengers possessing virtuallyinfinite lifetime.
Introduction: thermoelectric generators
Thermoelectric generators (TEGs),also called “thermoelectric converters”,are most ideally suited to generate elec-trical energy from industrial sources ofwasted heat. The history of thermoelec-tric generation brings us back to 1823,
when the German physicist Seebeckdiscovered that a voltage was devel-oped in a loop containing two dissimilarmetals, provided that the two junctionswere exposed to different temperatures.Thermoelectric generators of today aremade up of semiconductors. They con-tain a large number of p-type and n-typeminiature bars of thermoelectric material(see figure 1).
The reason for this design is that theSeebeck voltage, i.e. the thermoelectricvoltage generated by one thermocoupleat one-degree temperature differencebetween the “hot” and “cold” junctions,does usually not exceed 0.2mV. Thethermoelectric legs are arranged electri-cally in series, to generate the voltage
required for electronics, and thermally inparallel, to obtain the large temperaturedifference between the junctions.Featured with no moving parts, beingsmall in size and producing no pollu-tants, thermoelectric generators areattractive alternatives for the batteries or wiring of many applications. Thesecover industry, medical, consumer ortelecommunications areas, security sys-tems and fire alarms whenever naturalthermal gradients or industrial heat flowsare available for utilization.
Miniaturized and cost-effective TEGsare of particular interest for applicationsof wearable electronics, where wastedbody heat can be used to provide powerautonomy to ICs, sensing elements and
POWER GENERATION
Figure 1. Design of a typical thermopile.
www.powersystemsdesign.com 4342 Power Systems Design Europe March 2006
ples, standing on the bottom hot-platesilicon chip, must touch the indiumbumps formed on the top cold-platechip. Two chips form a sandwich withthe thermopile in between. However, traditional designs such as these sufferfrom a parasitic heat exchange betweenthe hot and cold plates, decreasing thethermal gradient on the thermopile down to tens of millikelvin and resultingin a negligibly low generated power.Therefore, IMEC proposes an innovativedesign that consists of making a rim inboth silicon chips. The thermopile of afew micrometer in size is to be fabricat-ed on top of this rim. Additional spacersabove the thermopile sandwich will beused to further decrease the influence ofthe parasitic heat flow inside the deviceon its performance.
Calculations based on this designshow an output voltage of 1—1.5V anda generated power of 1—2μW on aver-age for a watch-sized TEG built with2.5μm-tall polycrystalline SiGe thermo-couples. It is important to notice that,without the use of the rim, the generatedpower would have been more than 100times less at the same output voltage.The output parameters highly dependon the material used for the thermocou-ples and technological possibilities.Therefore, further improvement of the micromachined thermopile chips isexpected with an electrical productionup to 30μW per square centimeter of the skin.
Proof of concept: prototype with BiTethermopiles
The main advantages afforded bymicromachining for manufacturing thethermopiles are the small size of thethermopiles and their potentially lowcost. However, the demonstration of thewireless body area sensor nodes self-powered from the body can as well bedone with thermopiles available on themarket. Therefore, in parallel to thedevelopment of micromachined TEGs,the concept of thermal matching theTEG to the human body and to the airhas first been demonstrated with a non-MEMS prototype. This is however at theexpense of a slightly increased size andof significantly more cost of fabrication.Nevertheless, simultaneously, it candemonstrate the improvement of theenergy generation by placing the TEGon the artery.
In a first demonstrator of these ‘sec-ond-generation’ thermoelectric bracelets,48 thermopiles are used in total. Eachthermopile has a size of 8x9x2.4mm3
and is composed of 128 thermocouples.The BiTe thermopiles are composed intoa miniature 3-dimensional matrix tomatch its thermal resistance to the onesof the air and human body. That is whyIMEC’s first demonstrator was called ‘T-Matrix’. The power conditioning elec-tronics suitable for a TEG operating on ahuman body has been developed. Itincludes up-conversion and voltage sta-bilization. The TEG generates an aver-age of 100μW of useful electrical power
stored in two nickel-metal hydride(NiMH) batteries. The electronic mod-ules are mounted on a watchstrap andcompleted with a sensor layer, a micro-controller and a wireless transceiverthereby creating a wireless sensor nodemodule. This first prototype of a self-powered sensor node has been used to transmit several measured quantitiesto a nearby pc with a transceiver operat-ing at 2.4GHz in a pulse regime.Transmission of the data once per 15sgives enough time for complete energyrecovery to keep the batteries perma-nently charged.
A second demonstrator has been builtin 2005 with smaller dimensions, suchthat its volume does not exceed the oneof a typical man’s watch. In this design,the custom-made four-stage BiTe ther-mopile block consists of about 3500thermocouples with only 0.2mm cross-section of the thermoelectric legs. Eachcontact of two adjacent thermocouplelegs provides approximately 0.2mV ofgenerated voltage per one degree oftemperature difference between the hotand cold junctions. The generator pro-duces 100—200μW average power iflocated on the radial artery. The outputvoltage, nominally, is 1.2V. The wirelesssensor module on a flexible carrier cov-ers part of a watchstrap. It includes alow-power micro-controller that is usedto control duty-cycled sensing applica-tions and application-specific sensors,which process e.g. biopotential signalssuch as in electrocardiography (ECG),
POWER GENERATION
transceivers that operate at low power,not exceeding a few milliwatt. For exam-ple, TEGs that generate electricity fromhuman heat have been mounted in awristwatch to drive a digital watch. Theuse of TEGs for such applications ispreferable in indoor conditions, whereother more powerful renewable energysources such as sunlight or wind are notavailable. It should however be noticedthat thermoelectric generators usuallywork much better outdoor.
It is the aim of IMEC’s research todevelop cost-effective, reliable, minia-ture energy scavengers, built on MEMStechnology, as a power supply for abody area network. This body area net-work, in development as part of IMEC’sHuman++ program, consists of a set ofwireless sensors and actuators able toprovide health, sports, comfort and safety monitoring functions to the user.These sensor nodes typically require 50 to 100μW of power. The cheap andsmall-sized TEGs will enable a trulypower autonomous solution and avoidthe use of cumbersome batteries.
The human body as a heat generatorModeling a TEG on a human body
requires knowledge of the thermal prop-erties of the latter. The heat flow fromthe body is determined by many factors,such as the body thermal regulationmechanisms, the physical activity of theperson, his/her age and acclimatization,clothes and weather conditions. Thebody of a human being or a warm-
blooded animal has a non-uniform tem-perature distribution caused by its car-diovascular system and by the air con-vection around the body. As a result, theplace of attachment of the device to thebody plays an important role for thedensity of body heat on the skin avail-able for conversion into electricity.
Therefore, prior to the modeling anddevelopment of the TEG for this particu-lar application, the heat flow through thehuman skin and the thermal features ofthe body have been investigated. Theregulation increasing the local heatflows through the skin using a TEG isaccompanied by a possible feeling ofdiscomfort, which has been also investi-gated to make the devices acceptable to be worn. The research has been performed on 158 volunteers. To thispurpose, ‘first-generation’ thermopileconverters were used, consisting of a 3-layer stack of classical BiTe ther-mopiles supplied with a conventionalmulti-fin radiator of about 2x4x4cm3
size. The main results of this study aresummarized below.
First, it is clear that in case of forcedair convection (walking, presence ofwind …), the heat flow through the skinincreases significantly. To obtain such arise of heat flow in still air, IMEC’s TEGattached to the skin is finished with aradiator. This increases its contact areawith air, so that this surface exceeds thesurface of the skin covered by thedevice. In this way, the interface resist-
ance between the device and the air issignificantly decreased, allowing moreefficient heat transfer through the skin.In the experiment, the generators sup-plied with a radiator demonstrated up to 7 times larger heat flow than the natural one. Moreover, it has beenobserved that the heat flows “painlessly”extractable with a small-featured TEGsignificantly exceed the flows occurringon a human body without the generator.
Secondly, the place of attachment ofthe device to the body plays an impor-tant role for the magnitude of the heatflow. Besides the positive effect ofclothes, which thermally isolate most ofthe body surface, increase the skin tem-perature and cause larger heat flowsfrom the open surfaces (the hands anda head), the presence of arteries isresponsible for a significant variation ofthe body properties from place to place.The cardiovascular system affects boththe heat flow density on the skin and thethermal resistance of the body betweenits inner (deep) part and the skin sur-face. As an example, changing the loca-tion of the TEG from the watch’s placeto the one on the radial artery, i.e. theplace on a wrist which is used to meas-ure the pulse, almost halved the bodythermal resistance. For these reasons,the radial artery on the wrist has beenused as the most appropriate place forthe TEG, as it results in a larger heatflow density and consequently moreelectrical power generated. Finally, itwas observed that the heat flows up to20mW/cm2 on the outer side of the wristand up to 30mW/cm2 on the radial arteryin general do not cause a local thermaldiscomfort for a sitting person.
Modeling and design of the thermo-electric generator
The above results have been used tomodel and design the MEMS-basedTEG for application on the human body.The body features have been modeledas a serial variable equivalent thermalresistor. The final goal of IMEC’sresearch on thermoelectric generators isto use micromachined thermopiles, witha minimal feature size of 1μm. The ideaof using micromachined thermopiles isnot new: the self-supported thermocou-
Figure 2. Design of the poly-SiGe thermopile sandwich. Figure 3a. Demonstrator of IMEC’s second-generation TEG.
POWER GENERATION
Figure 3b. Electronic modules, mounted on a watchstrap.
www.powersystemsdesign.com 45
POWER CONTROL
44 Power Systems Design Europe March 2006
electromyography (EMG) and electroen-cephalography (EEG). The transmissionrate is increased to 0.5s-1, however, thedecreased power consumption in theelectronic module provides non-stopoperation on a human body.
Outlook: next-generation TEGs
BiTe versus SiGeBiTe thermopiles are expected to
generate more power than SiGe ther-mopiles. IMEC’s calculations on micro-machined BiTe thermopiles, inside thebuilding and at 22°C, show up to 30μWof generated power per 1cm2 of skin,while poly-SiGe may offer up to 5μWper 1cm2. However, the main target ofIMEC’s investigation is not the best per-formance, but the lowest cost, as theseTEGs are to replace the cheap batteriesused nowadays. In addition, polycrys-talline SiGe is the material that is moreextensively studied in microelectronics.Therefore, next-generation TEGs will befabricated using micromachined SiGethermopiles. The additional advantageis that the technology for poly-SiGe layers developed at IMEC provides avery low thermal conductivity of only0.03W/cm K. The advantage of usingmicromachined thermopiles is the largesurface density of thermocouples thatcan be achieved. Thanks to this featureand the use of IMEC’s novel design, itwill be possible to deliver the power at areasonably high voltage.
Technology for polycrystalline SiGethermopiles
IMEC has developed a process flowfor fabricating and assembling themicromachined TEG. The process flowstarts with etching microcavities underthe thermocouples and filling them withSiO2. This is followed by deposition andpatterning the SiO2 pads on top of theSiO2-filled microcavities. Then, p- and n-poly-SiGe legs are formed and alu-minum interconnects are made for hotand cold junctions. Deep ion reactiveetch of silicon is subsequently per-formed to fabricate the rim structure. Atthis point, the chip surface that isn’t cov-ered with the thermocouples or metallines, is the subject of a deep 0.25mmetch. After opening the side of the ther-mocouples, the sacrificial SiO2 layersare etched away. The top, a heat-spreading chip, represents patterned Alsquares covered with indium. The alu-minum layer is electrically isolated fromsilicon with a thin Si3N4 layer. Upon fab-rication of this structure, the top chip isalso etched to form a rim of the sameheight, i.e., 0.25mm.
In order not to destroy the thermopilemechanically during assembling thedevice and further exploitation, a num-ber of thermocouples are left with sacri-ficial oxide. These thermocouples serveas mechanical stoppers when mountingthe top chip on the bottom one. Theassembling of two chips is performedusing a benzocyclobutene layer on topof four pillars made on the chip corners.The assembled thermopile sandwichwill be mounted on a metal plate touch-ing the skin and supplied with a watch-strap. The radiator as well as the rest ofthe device will be protected with atouch- and shock-protecting grid similarto the one shown in figure 3. Fabricationof the poly-SiGe thermopiles based onthis process flow is currently ongoing.
IMEC has developed first prototypesof a thermoelectric generator scaveng-ing energy from wasted human bodyheat. The design is built on the basis ofa thermal model of the device, whichincludes the human body as one of its
important elements. Novel element ofthe thermal design is the presence of apillar/rim structure, on which the ther-mopile and the heat spreading structureare placed. This significantly decreasesthe parasitic heat exchange betweenthe hot and cold plates, resulting in use-ful output parameters. Prototypes of aTEG have been made using commercialBiTe thermopiles and have the size of atypical man’s watch. Output voltagenominally is 1.2 or 2.4V; the averagepower is about 100 – 200μW.
The final goal of this research is todevelop cost-effective miniaturizedTEGs built on MEMS technology. Theyare to power the variety of sensor nodesthat can be attached to a human skin,as well as the incorporated wirelesssensor modules transmitting measuredparameters to a nearby base stationand receiving the information for actua-tors from the station. Further researchfocuses on the development of micro-machined poly-SiGe TEGs, as they offera cheap solution. A process flow hasalready been developed and a firstdemonstrator run is being fabricated.
Contact: [email protected]
Figure 4. A corner of the chip contain-ing about 2500 poly-SiGe thermocou-ples forming a thermopile before etching the rim.
www.imec.de
POWER GENERATION
Economical lighting source is now available
New buildings are benefiting from economical LED lighting automated bylow-power wireless networks.
By Ofer Aluf, Technical Sales Manager, Future Electronics Europe
“Smart buildings” is the phraseused by engineers to describeoffice complexes, residential
blocks or factories that are built withautomation in mind. One driving forcefor automation is to reduce energy con-sumption. Intelligent control of lightingsources - for example, turning them offwhen there is no motion detected in aroom – promises to slash power costsand make a welcome contribution toreducing greenhouse gas emissions.
Coincidentally, a new, economicallighting source is now commerciallyavailable to building engineers whichruns at a fraction of the power of incan-descent light sources. Called High-power LEDs, these devices also benefitfrom rapid start-up and switch-off.These devices finally provide lightingengineers with an opportunity to movelighting out of the 19th Century.
The basis of building automation is asmart sensor network, allowing devicesto communicate intelligently. These sen-sors can then be used to detect andcontrol any number of devices. Typicalapplications range from smoke detec-tors, air conditioning, intruder alarmsand lighting.
To make them cost effective the sen-sors have to be cheap to make andinstall, and run at low power for long
periods with very low duty cycles. It alsohelps if the devices communicate wire-lessly, because that removes the needfor the kilometres of expensive wiring alarge office or residential block woulddemand. ZigBee, the low-power, lowdata rate, IEEE-based communicationsprotocol has been designed with exactlythis kind of application in mind.
High-power LEDs allied to a networkof ZigBee-enabled sensors endowssmart buildings with efficient, unobtru-sive and responsive lighting controlledby a reliable, robust, low-power meshnetwork able to service hundreds ofnodes. The “intelligence” added byZigBee allows the lighting system to beextended beyond a simple passive sys-tem. For example, high power LEDscontrolled by a network that includesmotion detectors could be used as asecurity measure to flood rooms withlight when an intruder is detected. Thiswould make it much easier to see theintruder on security cameras.
There are some challenges in imple-menting a ZigBee network controllingbuilding lights. These range from ensur-ing the efficient transfer of data, toreducing the power at each node of thecontrol network, and designing a powersupply for the high power LEDs.However, with guidance from a knowl-edgeable supplier and the use of proven
hardware and software from companiessuch as Freescale and Lumileds, thetask can be simplified.
A network for smart buildingsWhile there are other smart building
network technologies, ZigBee is the one gaining most traction. This is partlybecause it is backed by an Alliance ofpowerful silicon vendors and partlybecause it has been designed specifi-cally to be inexpensive to install and operate.
While ZigBee is a proprietary protocolbelonging to the Alliance, it is foundedon the IEEE 802.15.4 RF communica-tions standard. ZigBee operates in thelicence-free global 2.4GHz, European868MHz, or US 915MHz ISM (IndustrialScientific Medical) band. The data rateat 2.4 GHz is 250 kbit/s (10 channels),20 kbit/s (single channel) and 40 kbit/s(6 channels) for the European and USbands respectively.
Each ZigBee network must have atleast one network coordinator; this unitmaintains overall network knowledgeand requires the most computing powerand memory. The network also needs afull function device (FFD) to provide ini-tialisation, node-management and node-information storage. (It’s also possiblefor a FFD to function as a network coor-dinator.) The remaining nodes can then
www.powersystemsdesign.com 4746 Power Systems Design Europe March 2006
be simple, battery-operated reducedfunction devices (RFDs) with limitedresources. This keeps the cost downand reduces power consumption. EachZigBee network can have up to 254client nodes, plus the network coordina-tor or FFD acting as a master. In addi-tion, there can be up to 100 co-locatednetworks. (See Figure 1.)
ZigBee networks can use “beacon” or“non-beacon” configurations. Beaconmode is used when the network coordi-nator is battery-operated, because itallows the system to minimise its powerconsumption in extended mesh net-works. The fact that the clients knowwhen to communicate with each otherprevents clashes (and hence corrupted
packets) and the need for retransmis-sion. The network coordinator managesthe channel and arranges the times ofthe calls. A client registers with the coor-dinator and looks for any messages; ifnothing is pending, the client returns tosleep. Once the client communicationsare completed, the coordinator goes tosleep, saving power.
In addition, ZigBee’s network (NWK)layer incorporates an algorithm thatattempts to maximise quality of the end-to-end communication link, thus avoid-ing the need to frequency hop andretransmit lost packets. This also helpsto lower overall power consumption.
In contrast, the non-beacon mode isdesigned for peer-to-peer access. Thenetwork coordinator is usually poweredfrom the main source so its receiver ison constantly. Each client is autonomousand can initiate a communication at will,but could interfere with others. Forexample, the system might be used forsecurity systems where client units,such as intrusion sensors, sleep for99.999% of the time. The remote sen-sors wake up on a regular (althoughrandom) basis to announce their pres-ence to the coordinator. When an event
Figure 1. ZigBee network.
Figure 2. Pulse width modulation (PWM) control.
occurs, the sensor wakes up instantlyand transmits an alert.
In a lighting application, one end ofthe ZigBee wireless link in the switch-to-light link will have access to mainspower (the end controlling the high-power LED). However, the switch canbe battery powered. Such an arrange-ment suits a non-beacon mode wherebythe network coordinator allows clients tosleep for unlimited periods, enablingthem to save power.
Let there be lightManufacturer Lumileds has invested
considerable research effort andexpense to develop power LED technol-ogy. These devices offer many advan-tages over their incandescent rivals. Fora start, they are much more efficient:This is because an incandescent bulbhas to use much of the energy inputsimply to heat up the filament. That heatis wasted, and only a small proportion ofthe energy is emitted as light.
Apart from superior energy efficiency,high power LEDs have many otheradvantages over traditional lighting.These advantages include: Instant-start;no IR radiation or UV components to thebeam; no mercury in the light source;very long operating life (up to 100,000hours); and a compact source offeringunobtrusive lighting with minimal main-tenance costs.
However, there are some downsides.For example, compared to filamentbulbs or fluorescent tubes the powersupply challenges for high power LEDsare more complicated. In particular, thefast start-up of high power LEDs - vary-ing from 15 ns for AllnGaP-based LEDsto 20 ns for InGaN – dictates that thedesigner must consider issues such asmaintaining and monitoring the powersupply circuit input and output voltagewithin strict tolerances.
While powering traditional lightsources is straightforward, high powerLEDs require some special considera-tions. A LED is current-driven instead ofvoltage-driven. This means its drivercan be as simple as a series resistor,
although this is inefficient. Superiormethods include pulse width modulation(PWM) control, which also imparts finedimmer control. (See Figure 2.)
ZigBee is ideally suited to take advan-tage of PWM control. An instruction todim a light requires several packets tobe transmitted and received in the cor-rect sequence. An acknowledgementframe format provides active feedbackfrom the lighting wireless receiver unit tothe transmitter that the dimming datapacket was received without errors.
For specific advice on LED driver cir-cuit design, it is best to consult with themanufacturer or distributor. Future, forinstance, employs engineers that areconversant with hi-power LED powersupply requirements.
Don’t get overheatedApart from the power requirements of
this new generation of lighting, thedesign engineer must also understandthe challenge presented by the heatgenerated inside the device.
The emitter produces around 1W,which is dissipated partially as light, butprimarily as heat. While electrical over-load can rapidly degrade the LED, heatis a biggest enemy. White LEDs (themost likely to be used for building light-ing) are particularly vulnerable, becausethe heat degrades both the chip and thephosphor coating of the LED dome that“converts” the chip output to white light.
A good starting point when consider-ing the thermal challenge is to consultReference 1. This application briefdescribes how to estimate and calculatethermal resistances and operating tem-peratures.
The designer must take care wheninterpreting the data sheet; the lifetimeof the device is determined by the dietemperature during operation, and somemanufacturers make it somewhat diffi-cult to find this information. However,Lumileds, a major supplier of hi-powerLEDs, clearly specifies the lifetime of itsdevices based on die temperature(rather than ambient temperature).
Calculating LED life related to dietemperature allows the designer toselect the appropriate heatsink for theapplication. For example, if the productis destined to operate in an elevatedambient temperature environment, thedesigner can select a larger heatsink tokeep the die temperature the same asthat in a product used in circumstancesthat are more normal.
Design expertise availableFreescale, a member of the ZigBee
Alliance, manufactures proven chipsetsadhering to the IEEE standard andZigBee protocol. The company’s productcomprises an RF data modem IC oper-ating in the 2.4GHz, a low power 8-bitHCS08 Flash microcontroller, and soft-ware meeting current ZigBee protocol.The current product comprises two chips,but continuing development will see anintegrated solution on a single chip.
Maxstream is another ZigBee supplier.The company uses Freescale’s siliconfor assembled units using ZigBee wire-less communication. Both companiesprovide solutions suitable for controllinghigh power LEDs. These products, andmany others, are available from FutureElectronics. The company is also able toprovide advice and expertise on how toimplement ZigBee-controlled LED-basedbuilding lighting.
ZigBee is increasingly gainingmomentum in smart building applicationsbecause it adds “intelligence” while min-imising complexity, cost and power con-sumption. ZigBee allied to a new gener-ation of lighting in the form of high-powerLEDs provides lighting design engineerswith the ideal opportunity to bring build-ing lighting into the 21st century.
www.FutureElectronics.com
POWER CONTROL POWER CONTROL
48 Power Systems Design Europe March 2006
Giving CDMA cellular phones longer talk time
As more functions are added to 2.5G and 3G cellular phones, the trend has been for the poweramplifier (PA) to carry the transmission of large amount of high speed data. Higher data
rates inevitably increase the power required by a PA.
By Lei Feng, Senior Strategic Applications Engineer, Micrel Inc.
Deliberately controlling the powerdelivered to a PA is essential tomaintain battery life and obtain
the longest possible talk time. Figure 1illustrates a simplified diagram showingthe structure of a typical PA for aCDMA/WCDMA cellular phone. Thebias voltage provides a reference poten-tial to the amplifier. The VCC1 and VCC2,normally tied together to one power sup-ply with much higher output capability,drive the output stage to attain adequatetransmitting power.
In a typical power controlling scheme,and depending upon the signal quality ina certain area, the PA is powered eitherdirectly by the battery or through aDC/DC converter. When the maximumtransmitting power is required, then thePA power is connected to the batterydirectly with a MOSFET switch, whichbypasses the DC/DC converter and itsexternal inductor. This option offers twoadvantages. First, for the high-powermode, a MOSFET switch with very lowon-resistance can be used to power thePA with nearly the same voltage of thebattery, in order to avoid signal distor-tion caused by unexpected voltage dropout. Second, the DC/DC converter isonly required to deal with the power inlow power mode, which then allows for
a much smaller form factor for both theinternal switching elements and theexternal inductors.
This structure requires a number offeatures from the device: The DC/DCconverter must have a very high effi-ciency, the output voltage of DC/DCconverter must be able to be dynamical-ly adjusted to make the system easy tobe designed with different PAs, as wellas adaptive to different infrastructuresand the oscillating frequency of theDC/DC converter should be set to be faraway from the base band modulationfrequency of the cellular phone. In addi-tion, the transient speed from a low to
high power mode, or the opposite direc-tion, must be high enough and to get ashigh transmitting power as possible; thebypass MOSFET switch must have lowenough on-resistance to ensure a verylow drop out from the battery voltagewhen working at high power mode andthe entire circuit area should be as smallas possible.
Figure 2 depicts the power solutionoffered by the Micrel MIC2224. Itincludes a synchronous DC/DC convert-er for the low-power mode, with a veryhigh efficiency of more than 90 percent,and a low resistance bypass MOSFET,40mohm typically. The output voltage of
Figure 1. A Simplified Diagram of Power Amplifier.
PORTABLE POWER
www.powersystemsdesign.com 5150
NEW PRODUCTS
Linear Technology Corporationannounces the LTC3035, a 300mA verylow dropout (VLDO) linear regulator withinput voltage capability down to 1.7V.Featuring a low internal reference voltagewith corresponding adjustable output volt-age operation from 0.4V to 3.6V, the
LTC3035 also maintains an extremely lowdropout voltage of only 45mV at full loadcurrent. To allow operation at low inputvoltages, the LTC3035 includes an inte-grated charge pump converter that pro-vides the necessary headroom for theinternal LDO circuitry. This low input volt-
age capability enables performance inapplications ranging from Li-Ion or 2xAAalkaline cell to low input to low output volt-age conversion systems. The LTC3035’stight output voltage ±2% accuracy, lowquiescent and shutdown currents of100uA and 1uA, respectively, combinedwith fast transient response and smallsolution footprint with few external com-ponents, make it ideal for battery-pow-ered handheld devices such asBluetooth-enabled devices, cellularphones, media players, handheld medicaland industrial instruments.
The LTC3035 regulator optimizes sta-bility and transient response with lowESR, ceramic output capacitors as smallas 1uF. Internal safety circuitry includesshort-circuit and reverse output currentprotection, plus output current and ther-mal limiting.
www.linear.com
300mA VLDO Features 45mV the DC/DC converter can be digitallyadjusted by the DAC output of themicrocontroller, from 0 to 3.6V. Whenthe DAC voltage is higher than 1.2V,then the device will automatically switchinto the high-power mode, turning on thebypass MOSFET and shutting down theDC/DC converter. The oscillating fre-quency of the DC/DC converter is fixedat 2MHz and hence, will not cause inter-ference. This high frequency, togetherwith Micrel’s patented compensationscheme, provides stable operation withworld smallest external components,requiring only tiny 2.2uH inductor and1uF output capacitor. Experiments inthis area have shown that the abovepower supply system can increase valu-able talk time by up to 40 percent, there-by significantly increasing talk time andmaking Micrel’s MIC2224 an fitting solu-tion for today’s demanding cellularphone applications.
Figure 2. Micrel Power Solution for PA. www.micrel.com
PORTABLE POWER
Linear Technology introduces theLTC2970, a dual I2C power supply moni-tor and margining controller designedfor digital management of power sup-plies in high-availability systems. TheLTC2970 offers the best melding of digi-tal and analog for digital power manage-ment. The I2C digital interface, 14-bitADC, highly accurate reference and cur-rent output DACs give digital power sup-ply designers what they want: digital
control of an analog power supply. TheLTC2970 works with most any powersupply, allowing designers to choose theoptimal DC-DC converter with an analogcontrol loop that provides smooth con-trol of the output voltage and fast tran-sient response. An on-chip referenceand 14-bit Δ∑ A/D converter ensureaccurate measurements of supply volt-ages, load currents or temperature. Twovoltage-buffered 8-bit DACs drive the
supplies’ feedback nodes for improvedaccuracy or can be programmed by aslow, linear voltage servo to trim andmargin the output voltages. This makesthe LTC2970 useful in determining thesensitivity of the power supply duringthe prototype phase or in production totest for manufacturing variations.
The superior accuracy of the ICallows it to precisely servo each supply’soutput voltage over a wide range ofoperating conditions, while integratingall the vital functions in a compact 4mmx 5mm QFN package. Extensive, user-configurable fault monitoring providesincreased reliability by alerting a sys-tem’s host to incipient failures beforethey occur. The LTC2970’s Δ∑ architec-ture was specifically chosen to averageout power supply noise and allow toignore fast transients.
I2C Power Supply Controller
www.linear.com
Power Systems Design Europe March 2006
www.powersystemsdesign.com 53
NIC Components Europe hasintroduced four new ranges ofcurrent sensing surface mountresistors. The NCSR, NCST,NCSP and NCSW series addressthe rapidly growing need for cur-rent sensing in power manage-ment and control applications inlow voltage, high current circuits.The trend towards smaller hand-held and portable electronicsequipment has also increasedthe need for ultra-small currentsensing resistors.
The NCSR and NCST seriesare precision thick film devicesthat are available in case sizesfrom 2512 down to 0402 (NCSTseries). The NCSP series mean-while uses a stable precisionconductor construction within asurface mountable moulded flat
pack. The NCSP series is available incase sizes from 5724 down to 2512.Devices from the NCSW series utilize athin film construction that enables themto achieve precision resistancetoler-ances, low noise, and long-term stabili-ty. The reverse termination format of theNCSW series gives increased heat dis-sipation to three Watts. Case sizesavailabl are either 0815 or 0830.
All devices from the new ranges ofcurrent sensing resistors comply withEU lead-free directives that come intoforce from July 2006 and are fully com-patible with Pb-free reflow processes.Samples and sample kits are availablefrom NIC.
Ultra-Stable Current Sensing Resistors
www.niccomp.com
52 Power Systems Design Europe March 2006
ON Semiconductor has introducedthree new low resistance analog switch-es for portable and wireless audio appli-cations. Offered in lead-free (Pb-free)Thin QFN / Thin DFN packages that uti-lize between 1.2 mm2 and 4.7 mm2 of
board space, these 6-pin, 10-pin and16-pin devices are the industry’s small-est and highest performance audio analog switches.
The three new high performanceaudio analog switches are designed forhigh-current switching of an audio signalin portable and wireless applicationswith low operating voltages. The devicesare ideal for higher power audio applica-tions that require low on-resistance(Ron) for improved power efficiency.
The NLAS3799MNR2G is a low volt-age, ultra low Ron, Dual Double Pole-Double Throw (Dual DPDT) switch. Itachieves total harmonic distortion of0.11% and low Ron of 0.35 Ohm allow-ing for superior audio performance andlow power consumption.
The NLAS5223MNR2G is a low volt-
age, ultra low Ron, Dual Single Pole-Double Throw (Dual SPDT) switch. Thisanalog switch has enhanced lower Ronperformance and has a 70 percentsmaller footprint than the very popularNLAS4684MNR2G. It achieves totalharmonic distortion of 0.12% and lowRon of 0.35 Ohm allowing for superioraudio performance and low power consumption.
The NLAS5123MNR2G is a 1 ohm,Ron, Single SPDT analog switch with0.012 % total harmonic distortion andbreak before make capability. It is avail-able in a Pb-free, 6-lead, Thin DFN thatmeasures 1.2 mm x 1.0 mm x 0.75mmand utilizes 53 percent less board spacethan competitor products.
Smallest Packaged Analog Switches
www.onsemi.com
National Semiconductor expanded itshigh-performance precision amplifierportfolio with the addition of three highcommon-mode difference amplifiers.
Designed for broad-based industrial,medical and telecommunication applica-tions, these new amplifiers meet therequirements for accurate current sens-ing measurements in products such asbase stations, notebook PCs and sen-sor controls in industrial applications.
The LMP8275 and LMP8277 highcommon-mode amplifiers and LMP8276high common-mode bidirectional ampli-fier join National’s LMP (linear monolith-ic precision) product family, whichdetects, amplifies and filters small differential signals in the presence ofhigh common-mode voltages.
The very low offset voltage (less than2 millivolts) and offset drift (less than 30microvolts/degrees Celsius) of theseproducts allow for accurate differentialsignal conditioning of small signals, withminimal voltage offset error through theentire temperature range. Additionally,the extended operating temperaturerange of -40 degrees Celsius to +125degrees Celsius ensures these amplifierscan be used in extreme conditions, suchas those found in industrial applications.
High-Performance Precision Amplifiers
www.national.com
Analog Integration Corporation islaunching a series of USB Power SwitchICs, called AIC1525/AIC1526/AIC1528/AIC1529, for self-powered and bus-powered applications. The high-sideswitch MOSFET with 70 mΩ and110mΩ RDS(ON), meets USB voltagedrop requirements for maximum trans-mission wire length. They provide appli-cations with benefits of circuit reliabilityand low cost by eliminating the need forexternal components.
AIC1525 and AIC1526 are 500mAUSB power switch IC that are one channel and two channels respectively.AIC1528 and AIC1529 are 1A USBpower switch that are two channels andfour channels respectively. A multi-pur-pose open-drain fault flag output indi-cates over-current limiting, thermal shutdown, or under voltage lockout foreach channel. These devices provide allprotection functions: over-current limit-ing, short-circuit protection, thermal
protection, and under voltage lockout. Enable active-high and active low
make shutdown control by firmwaremuch easier for users. Low on-statesupply current, typical 75μA for AIC1525and 110μA for AIC1526/AIC1528 and220μA for AIC1529, makes thesedevices ideal for low standby powerapplication.
USB Power Switch IC
www.analog.com.tw
NEW PRODUCTS
The LDS Series inverters from Endicott Research Groupprovide a high efficiency DC-AC inverter in a compact formfactor for use with a range of LCD panel sizes from 6.4˝ to12.1˝ diagonal.
Measuring only 5.24˝ (133.1 mm) long x 1.22˝ (31.0 mm)wide and less than 9 mm high, LDS Series inverters provideup to 12 watts of output power, with direct display connectionand wide range PWM dimming.
LDS Series inverters are designed to power up to fourCCFLs (cold cathode fluorescent lamps) with a combinedpower of 12 watts. An external analog control interfaces withan on-board pulse width modulator (PWM) to provide dim-ming control. LDS inverters can reliably dim to less than 5%of duty cycle. Operating temperature is –20°C to +70°C.
These inverters also offer expanded output connectoroptions to meet the needs of both the OEM as well as systemintegrators and value-added resellers of LCDs.
Compact Inverter for LCDs Backlit
www.ergpower.com
NEW PRODUCTS
www.powersystemsdesign.com 5554 Power Systems Design Europe March 2006
NEW PRODUCTS NEW PRODUCTS
Anderson Power Products announcesits new PowerMod HP (high power) “B”series connector family, featuring touch-
safe female housings, integral positivelatches and cable strain relief. Thesesafety features, combined with the easeof connector assembly, establish a newstandard for cost effective high powerconnectors.
APP’s PowerMod HP “B” Series con-nector is rated over 350 amps for appro-priate applications and to 250 amps at a30 ºC temperature rise. The productaccommodates American wire sizesfrom 1/0 to 4/0 AWG and metric wiresfrom 50 to 95mm2. These connectorsuse APP’s patented Sterling contacttechnology that offers low electrical
resistance, provides a minimum of 500mating cycles and is rated for circuitinterruption (true hot-plug).
The unique latching system, with dis-tinct blue buttons for clear identification,offers superior security and ergonomics.These connectors are IP 20 rated (touchsafe) for user safety, and the integralcoding key provides further protectionby allowing the user to configure uniquemating of up to 6 individual connectors.
Touch-Safe Connector
www.andersonpower.com
Tyco Electronics Power Systemsannounced the release of its EQW010-040 series DC-DC converters, an exten-sive line of new generation, eighth brick,DC-DC power modules designed forregulated single output voltages rangingfrom 1.0Vdc to 12Vdc. The EQW seriesdelivers up to 10A at 12Vout, 20A at 5V,30A at 3.3V, 35A at 2.5V and 40A of out-put current for 1.8V and lower outputvoltages. These converters are suitedfor use in distributed power architec-tures, wireless networks, access andoptical network equipment, enterprisenetworks for powering the latest genera-tion ICs (DSP, FPGA, ASIC), and micro-processor powered applications.
EQW010-040 Series converters oper-ate over a wide input voltage range of36 to 75 Vdc, providing a single, pre-cisely regulated output with full load effi-ciency of 92% at 3.3V output. This highefficiency converter series employs half-bridge conversion topology with highlyoptimized synchronous rectification andincorporates innovative edge-platingand packaging techniques to deliversuperior thermal performance. Built-infiltering for both input and output mini-mizes the need for external filtering.
The EQW010-040 series is rated forwide operating temperature range of -40°C to - 85°C in an industry standardeighth-brick package of 57.9 mm x 22.9
mm x 8.5 mm. Standard featuresinclude: remote on/off, remote sense,monotonic start-up under pre-bias con-ditions, zero reverse current duringstart-up and shutdown, over-tempera-ture protection, input under/overvoltageprotection, and output overcurrent/volt-age protection. Surface mount intercon-nect and a base plate for superior thermal performance are available asoptions. The converters are designed tobe fully compliant to RoHS EU Directive2002/95/EC.
High-Power Eighth Brick DC-DC Converter
www.power.tycoelectronics.com
Phihong USA has developed a redun-dant power source with up to 180Power-over-Ethernet ports to meet theneeds of telecom applications, such asVoIP systems. The RPS accepts three
500-watt power supplies for poweringVoIP phones, DC UPS, and lighting sys-tems with single UPS. A typical VoIPphone draws less than 8 watts. With1500 watts available, 180 PoE phonescan be supported from this redundantsource.
Each output in the redundant powersource is individually protected againstoverloads causing overheating of wiringfrom excessive current, thus fully pro-tecting the system against overload,over-temperature and over-voltage. Itfeatures diagnostic capabilities andLEDs next to each connector. The RPS
was designed to allow easy connectionof a battery plant for full DC UPS capa-bility for VoIP phone systems or networkswitches. A single battery plant can pro-vide a UPS function for over 180 IPphones or a complete rack of networkswitches.
The redundant power source is 17.25inches x 13.77 inches x 1.75 inches,and it weighs 2.5 pounds.
www.phihong.com
Power Supplies for VoIP
A high voltage MOSFET from ZetexSemiconductors has been introduced tohandle the requirements of pre-biassupply circuitry. A 450V enhancement
mode N-channel device, theZXMN0545G4 is used in a simple linearregulator to supply PWM ICs at start-up,and is disabled once the converter isfully on. Compared to alternative resis-tor dependent solutions, the MOSFETbased approach improves system effi-ciency and reduces start-up time.
To maximise resistance to high volt-age creepage, the MOSFET is providedin a unique 4-pinned SOT223-package.By simply disconnecting one of the twoconventional drain pin positions, thedevice’s new leadframe design signifi-cantly extends inter-pin spacing, which
helps designers comply with UL and CEcreepage distance specifications.
Characterised by low on resistance—a maximum of 50Ω—and supportingcontinuous drain currents up to 140mA,and pulsed currents of 600mA, the tran-sistor offers a highly efficient power han-dling capability. Switching speed is alsofast, with turn-on and rise times speci-fied at 7ns.
Power Supply Start-Up MOSFET
www.zetex.com
International Rectifier has introducedvery high efficiency 75V and 100VHEXFET power MOSFETs in the TO-220 package that enable a part countreduction of 30% or more in secondary
synchronous rectification, full-bridgetopology power supplies compared tocompeting devices in the same package.
The 75V MOSFETs are designed toshrink circuit size and increase powerdensity in high power server AC-DCswitch-mode power supplies (SMPS)with 12V output or in 48V rail ORing cir-cuits. The new 100V devices suit highpower flyback secondary rectification oroffer enhanced primary-side efficiency inhigh power telecom isolated 48V DC-DCconverters. In addition, the new MOSFETscan be used in stepper motor andbrushless DC motor drive applications.
The IRFB3077PbF is a 75V MOSFETwith 3.3mOhm maximum device on-
resistance, and enables a 30% partscount reduction (from ten TO-220devices to seven TO-220 devices), witha reduced PCB area and heatsinking forhigher power density in 3kW serverSMPS with 12V output.
The IRFB4110PbF is a 100V MOS-FET with 4.0mOhm maximum deviceon-resistance, and can slash compo-nent count in half, reducing PCB areaand reducing heat sink size.
The new synchronous HEXFETMOSFETs are available now and arelead-free (PbF) and are RoHS-compliant.
www.irf.com
Powerstax announces introduction ofthe new A3600 series of ultra low pro-file, 1U high 19” rack mount, config-urable AC-DC power supply. Capable ofproviding up to 3,600W output powerthe A3600 offers users multi-output
“custom” power solutions withoutextended lead times and high NRE costs.
The A3600 employs a modular con-struction that has been developed todeliver advanced market-leading versa-tility using ultra-high efficiency (>90%)standard products from the Powerstaxrange. In a very compact, ultra low pro-file 1U high 19“ rack mount package351mm deep, the A3600 offers combi-nations of single or multi-output, regulat-ed DC power from a universal inputmains supply of 85-264Vac. Input andoutput connection may be specified atfront or rear and may be cable entry,connector or safety stud as required.
With up to 18 isolated and adjustableoutputs, it is possible to individually mar-gin, enable, parallel or stack the outputsto provide literally millions of power vari-ants. Features include zero load opera-tion and fully floating outputs that havestandard output voltage ranges from1.5V to 58V, few electrolytic capacitors(all long life), local and remote adjust-ment, and user adjustable current limitand inhibit/enable functions.
www.powerstaxplc.com
Configurable Multi-Output Power Supply
Synchronous Rectification MOSFETs
www.powersystemsdesign.com 5756 Power Systems Design Europe March 2006
NEW PRODUCTS
Companies in this issue
Company Page Company Page Company Page
ABB Lyon . . . . . . . . . . . . . . . . . . . . . . .50ABB Lyon . . . . . . . . . . . . . . . . . . . . . . . . .1ABB Switzerland . . . . . . . . . . . . . . . . .C3ABB Switzerland . . . . . . . . . . . . . . . . . .1,4Advanced Power Technology . . . . . . .33Anagenesis . . . . . . . . . . . . . . . . . . . . . . .1Analog Devices . . . . . . . . . . . . . . . . . . .52Anderson Power Products . . . . . . . . . . .54Ansoft . . . . . . . . . . . . . . . . . . . . . . . . . .13Ansoft . . . . . . . . . . . . . . . . . . . . . . . . . . .1APEC . . . . . . . . . . . . . . . . . . . . . . . . . . .41Artesyn Technologies . . . . . . . . . . . . . .1,4Bergquist . . . . . . . . . . . . . . . . . . . . . . .29Code Mercenaries . . . . . . . . . . . . . . . . .34CT-Concept Technology . . . . . . . . . . .21Curamik . . . . . . . . . . . . . . . . . . . . . . . .27Danfoss . . . . . . . . . . . . . . . . . . . . . . . .30Danfoss . . . . . . . . . . . . . . . . . . . . . . . . . .1Endicott Research Group . . . . . . . . . . .53EPCOS . . . . . . . . . . . . . . . . . . . . . . . . .39Eupec . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Fairchild Semiconductor . . . . . . . . . .C2Fairchild Semiconductor . . . . . . . . . . . .1,6Future Electronics . . . . . . . . . . . . . . . . .45ICE Components . . . . . . . . . . . . . . . . . .33IMEC . . . . . . . . . . . . . . . . . . . . . . . . . . .40Infineon Technologies . . . . . . . . . . . . . . .1International Rectifier . . . . . . . . . . . . .C4International Rectifier . . . . . . . . . . . . .1,55Intersil . . . . . . . . . . . . . . . . . . . . . . . . . . .1iSuppli . . . . . . . . . . . . . . . . . . . . . . . . . .14IXYS . . . . . . . . . . . . . . . . . . . . . . . . . . .15LEM Components . . . . . . . . . . . . . . . . .3LEM Components . . . . . . . . . . . . . . . . . .1Linear Technology . . . . . . . . . . . . . . . . .5Linear Technology . . . . . . . . . . . . .1,37,51Maxwell . . . . . . . . . . . . . . . . . . . . . . . . . .6Micrel . . . . . . . . . . . . . . . . . . . . . . . . . .11Micrel . . . . . . . . . . . . . . . . . . . . . . . .48,50Microsemi . . . . . . . . . . . . . . . . . . . . . . .18National Semiconductor . . . . . . . . . . .31National Semiconductor . . . . . . . .1,24,52
Northrup Grumman . . . . . . . . . . . . . . . . .6NIC Components . . . . . . . . . . . . . . . . . .53Ohmite . . . . . . . . . . . . . . . . . . . . . . . . . . .1On Semiconductor . . . . . . . . . . . . . . .1,52PCIM Europe . . . . . . . . . . . . . . . . . . . .49Phihong . . . . . . . . . . . . . . . . . . . . . . . . .54Power Integrations . . . . . . . . . . . . . . . .7Power Integrations . . . . . . . . . . . . . . .1,16Power Stax . . . . . . . . . . . . . . . . . . . . . .55Semikron . . . . . . . . . . . . . . . . . . . . . . .25Semikron . . . . . . . . . . . . . . . . . . . . . . . . .1ST Microelectronics . . . . . . . . . . . . . . . . .4SynQor . . . . . . . . . . . . . . . . . . . . . . . . . .1Texas Instruments . . . . . . . . . . . . . . . .19Texas Instruments . . . . . . . . . . . . . . .1,28Tyco Electronics . . . . . . . . . . . . . . . . .1,54Wurth . . . . . . . . . . . . . . . . . . . . . . . . . .53Yokogawa . . . . . . . . . . . . . . . . . . . . . . .56XP Power . . . . . . . . . . . . . . . . . . . . . . . .56Zetex . . . . . . . . . . . . . . . . . . . . . . . . . .4,55
Please note: Bold—companies advertising in this issue
An advanced calculation function hasbeen introduced as an option for theYokogawa WT3000 precision poweranalyser to support customer require-ments for more advanced and complexpower analysis capabilities.
The new /G6 Option adds the capabil-ity for IEC61000-3-2 compliant harmonicmeasurements, wide bandwidth harmonicmeasurements, FFT calculations andwaveform mathematical function, plusthe ability to store transient waveform data.
In the IEC harmonic measurement
mode, the instrument can be used withYokogawa’s new 761922 harmonicmeasurement software to perform testsconforming to IEC 61000-3-2 rev. 2.2. Itcomplies with the latest IEC61000-3-2and IEC61000-4-7 requirements, includ-ing 10/12 cycle waves at 50/60Hz, inter-harmonic measurements and grouping.
The wide-bandwidth harmonic meas-urement function allows harmonic analy-sis on waveforms with a fundamentalfrequency range from 0.1 Hz to 1 kHz(or 0.1-10 Hz using an external sam-
pling clock). Measurements can bemade up to the 50th-order harmonic at a1 kHz fundamental frequency, or up tothe 20th-order harmonic in the rangefrom 1.1 kHz to 2.6 kHz.
Two FFT calculations can be per-formed simultaneously on waveformdata of measured voltage and current,with a user-selectable minimum resolu-tion of 1 Hz or 10 Hz. FFT analysis canbe performed at up to 100 kHz.
www.yokogawa.com
Precision Power Analyser
Aimed at telecoms, mobile communi-cations and networking applications with48VDC input for onboard power, XPPower’s SWX series of low powerDC/DC converters includes the world’ssmallest footprint 30W version. The low cost converters save valuable board space.
The 10 to 30W SWX series is aimedat optical fibre access equipment, ADSLapplications, routers, switches, and cel-lular base stations where small size,high efficiency, high operating tempera-
tures, low profile, and surface mountcapability are requirements.
Obviating the need for fans, the con-vection-cooled converters have an operating temperature range of -40 to+85 degrees C. Their 91% efficiencyensures that minimal heat is generated,providing increased reliability and sim-plifying cooling arrangements.
Useful in applications where PCBsare stacked closely, the converters havea low profile. The 10, 15 and 20W mod-els have a footprint of 38.7 x 27.2 x
5mm, and the 30W version has a foot-print of 38.7 x 31.2 x 8mm. SWX DC/DCconverters employ synchronous rectifi-cation to enhance efficiency. The inputvoltage range for 48V models is 36—76VDC, and the 24V input versionsaccept a voltage input range of 18 to36VDC. Output voltages are from 1.2Vto 15.0V.
www.xppower.com
Smallest Telecom 30W DC/DC Converter
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