Designer's Guide to Isolation Circuits

8/9/2019 Designer's Guide to Isolation Circuits

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Designer’s Guide

to Isolation Circuits


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About This Designer’s Guide

Hewlett-Packard optocouplerscan be used in an array of

isolation applications rangingfrom power supply and motorcontrol circuits to data communi-cation and digital logic interfacecircuits.

To help you choose and designwith Hewlett-Packard isolationcomponents, this Designer’sGuide contains 50 popularapplication circuits and recom-mended HP optocouplers.

This handbook begins with aselection guide followed bysections discussing criticaloptocoupler design parameterssuch as Insulation and WithstandVoltage, Regulatory AgencySafety Standards, Common-Mode

Transient Rejection, Product Lifeand light emitting diode (LED)aging. The rest of the guideconsists of application circuits.

Each application circuit isaccompanied by:

1. A brief description.

2. Highlights of circuitperformance.

3. Circuit benefits.

4. References for additionaltechnical information.

5. A list of alternative HP partsindicating comparably per-forming products available invarying package styles formaximum design flexibility.

How to Use This GuideSeveral indexes are included tohelp locate applications andproducts.

• The table of contents lists the50 applications by their generaldescription.

• An alphanumeric index lists allapplications by title.

• Selection Guides in the form of tables contain basic productspecifications which allows you

to quickly select the productsmost suitable for your

applications.Most data sheets for productsrecommended here can be foundin Hewlett Packard’sOptoelectronic Designer’s Cata-log, or they may be ordered fromyour local HP representative.

How to Order To order any component in thisguide or additional applicationsinformation, call your authorized

HP distributor nearest you.

Although product informationand illustrations in this guidewere current at the time it wasapproved for printing, Hewlett-Packard, in a continuing effort tooffer excellent products at a fairvalue, reserves the right tochange specifications, designs,and models without notice.


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Design Considerations .............................................................................................................................................12Insulation and Regulation of Optically Coupled Isolation Devices .............................................................12Common-Mode Transient Rejection.................................................................................................................17LED Degradation Over Time .............................................................................................................................22Guidelines for Printed Circuit Board Assembly and Layout.........................................................................25

Digital Logic Interface/Level Shifting Applications .......................................................................................27 TTL Interface with Series LED Drive ...............................................................................................................27Level Shifting/TTL Interface with Shunt LED Drive ......................................................................................28Low Power 100 kBd CMOS Interface...............................................................................................................29Low Power 8 MBd CMOS Interface..................................................................................................................30

50 MBd CMOS Interface.....................................................................................................................................313 V Logic Interface/Battery Operated Applications........................................................................................32

Data Communication Applications ......................................................................................................................33Isolated RS-232C Interface.................................................................................................................................33Isolated RS-422 Interface ...................................................................................................................................34Isolated RS-485 Bus Interface............................................................................................................................35Isolated Device Net/CAN Interface...................................................................................................................36Isolated 20 mA Current Loop Interface............................................................................................................37Multidrop Line Receiver .....................................................................................................................................38Isolated Balanced Line Receiver - Circuit No. 1 .............................................................................................39Isolated Balanced Line Receiver - Circuit No. 2 .............................................................................................40Isolated Tri-State Line Driver ............................................................................................................................41

Isolated Unbalanced Line Receiver ..................................................................................................................42Profibus DP 12 MBd Interface...........................................................................................................................43

Telecommunications Applications .......................................................................................................................44 Telephone Ring Detection..................................................................................................................................44ISDN Interface .....................................................................................................................................................45

Telephone Pulse Dialing and On/Off Hookswitch Circuit.............................................................................46 Telephone Line Selection Circuit......................................................................................................................47

Motor Control Applications ...................................................................................................................................48Motor Current Sensor/Integrated Isolation Amplifier ...................................................................................48Isolated Gate Driver for IGBT/MOSFET - Circuit No. 1 ................................................................................49Isolated Gate Driver for IGBT/MOSFET - Circuit No. 2 ................................................................................50Isolated Gate Driver for IGBT/MOSFET - Circuit No. 3 ................................................................................51Isolated Gate Driver for IGBT/MOSFET - Circuit No. 4 ................................................................................52Isolated Base Drive for Bipolar Power Transistors/Darlingtons..................................................................53Isolated High-Voltage Sensor - Circuit No. 1 ...................................................................................................54Isolated High-Voltage Sensor - Circuit No. 2 ...................................................................................................55Motor Control Isolated A/D ...............................................................................................................................56

Table of Contents (1)


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Analog Applications ..................................................................................................................................................57Single-Supply Isolation Amplifier/Power Supply Feedback .........................................................................57Precision Isolation Amplifier for Unipolar Signals ........................................................................................58Isolation Amplifier for Bipolar Signals - Circuit No. 1...................................................................................59Isolation Amplifier for Bipolar Signals - Circuit No. 2...................................................................................60Isolated 4-20 mA Analog Current Loop Transmitter/Receiver......................................................................61AC-Coupled Isolated Amplifier .........................................................................................................................62Isolated Video Interface .....................................................................................................................................63Differential DC Isolation Amplifier...................................................................................................................64Servo Type DC Isolation Amplifier ...................................................................................................................65Analog Signal Coupling Using Pulse-Width Modulation ................................................................................66

Analog Signal Coupling Using Voltage-to-Frequency Conversion................................................................67Analog Signal Coupling Using A/D Converters ...............................................................................................68Analog Signal Multiplexing................................................................................................................................69Analog Signal Sensing - Flying Capacitor Technique.....................................................................................70

Industrial Applications ............................................................................................................................................71AC/DC Voltage Threshold Sensing....................................................................................................................71Low Power AC/DC Industrial Switching..........................................................................................................72Optical Isolation in Flat-Panel Displays...........................................................................................................73Gain Selection for Op-Amps Circuits ...............................................................................................................74Low Power Alarm Control Circuit ....................................................................................................................75Relay Coil Driver .................................................................................................................................................76

Power Supply Applications .....................................................................................................................................77Optical Isolation in a Switching Power Supply - Circuit No. 1.....................................................................77Optical Isolation in a Switching Power Supply - Circuit No. 2.....................................................................78

Optocoupler Applications Index ...........................................................................................................................79

Table of Contents (2)


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Design Considerations

ability of the optocoupler to

prevent the distortion of datathrough the suppression andfiltration of common-modetransients. A further discussion of signal isolation can be found inthe section entitled “Common-Mode Transient Rejection.”

The effects of repeated long-termhigh-voltage stress between inputand output of an optocoupler hascontinued to be an area of uncertainty. Much of the technicalemphasis has been on the abilityof optocouplers to withstand one-time short-term high-voltagetransients (e.g., U.L. 1 minutedielectric voltage withstandrating). Hewlett-Packard hasconducted extensive operatinglife tests to determine the effectsof continuous high-voltage stress,both transient as well as steady-state, on the degradation of insulating performance. On

completion, the test data wasanalyzed to determine safeoperating areas for steady-stateinput-output high-voltage stress.

The boundary conditions, asshown in Figures 1, 2, 3, havebeen defined by Hewlett-Packardas Endurance Voltage. The lowerregion refers to the safe operat-ing area for the application of continuous steady-state ac and dcinput-output voltage stress, or

The primary purpose of opto-

coupler devices is to provide bothelectrical insulation and signalisolation. The popularity of Hewlett-Packard's product offeringcan be accredited to cost-effectiveinnovations in these areas. Yetthere exists a surprising level of misunderstanding regarding thesetwo terms from both vendor anduser alike. The discrepancies thatexist within the worldwideregulatory community add to thefrustration level for manydesigners. This discussionattempts to help the designercapitalize on HP’s knowledge.

Insulation Defined The electrical insulating capabilityof an optocoupler, sometimesreferred to as withstand voltage,is determined by its ability toprotect surrounding circuitry, aswell as itself, against physicaldamage resulting from different

voltage potentials. This potentiallydamaging phenomena can besystem induced (e.g., motor railvoltage) or externally coupled(e.g., lightning pulse). Theinsulating material between inputand output as well as the packag-ing technology are the primarydeterminants of withstand voltagecapability. In contrast, signalisolation, although sharing somecommon causes, defines the

working voltage, and the middle

region to transient voltage stress.Operation above these regionshas shown to cause wear-outeither in functionality or insulat-ing capability and is not recom-mended. Endurance Voltage isbased on the inherent propertiesof Hewlett-Packard optocouplersthat utilize unique packagingtechnologies and does not applyto products manufactured byother vendors. In addition, asthese tests do not take intoconsideration particularequipment use conditions,Hewlett-Packard recommends thedesigner consult the appropriateregulatory agency guidelines todetermine applicable workingvoltage. For an in-depth discussionon Endurance Voltage, consultHewlett-Packard Application NoteAN1074.

Regulatory Environment

Because electrical insulation is afunction of safety, optocouplerperformance, both at componentand system levels, is often subjectto regulatory requirements andapprovals that vary according tocountry as well as industry. Mostagencies are a mixture of govern-mental and private organizationswith industry representation.Some common regulatoryagencies are listed in Table 9.

Insulation and Regulation of Optically CoupledIsolation Devices


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Category 1 Optocouplers Category 2 Optocouplers:

WARNING: In all cases where regulatory compliance is required, working voltage as defined by theregulatory agency cannot be exceeded.

Category 3 Optocouplers:

Figure 3. Recommended Safe Operating Area forInput-Output Voltage-Endurance Voltage forCategory 3 Optocouplers.

Figure 4. Optocoupler’s Insulation Parameters.

Figure 1. Recommended Safe Operating Area for Input-Output Voltage-Endurance Voltage for Category 1Optocouplers.

Figure 2. Recommended Safe Operating Area for Input-Output Voltage-Endurance Voltage for Category 2Optocouplers.


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Table 9

COMMON REGULATORY AGENCIES

Name Country Abbreviation

Verband Deutscher Electrotechniker Germany VDE

Underwriters Laboratories United States UL

Canadian Standards Association Canada CSA

British Standards Institute United Kingdom BSI

Norge Elektriske Materielkontrol Norway NEMKO

Danmarks Elektriske Materielkontrol Denmark DEMKO

Svenska Elektriske Materielkontrollanstalten AB Sweden SEMKO

Sahkotarkastuskeskus Elinspektionscentralen Finland SETI

Currently, little conformity existsbetween the various agenciesregarding mechanical configura-tions and electrical test require-ments. Within the EuropeanUnion, however, standardizationof equipment as well as componentlevel specifications is in progress.In the interim, testing andapproval according to equipmenttype and environmental factorsmust be obtained according to

the control documents of eachcountry. The InternationalElectrotechnical Commission(IEC), with worldwide representa-tion, provides a forum forgenerating technical standards.

The European Committee forElectrotechnical Standardization(CENELEC), has EuropeanCommission authority to adoptIEC standards as EuropeanNorms (EN), with the force of law.

Common Terms

External Clearance The shortest distance throughair, between conductive inputand output leads, measured inmm. Refer to Figure 4.

Comparative Tracking Index(CTI)

Outer molding material charac-terization in the presence of aqueous contaminants. Thehigher the CTI value, the moreresistant the material is toelectrical arc tracking. CTI isoften used with creepage bysafety agencies to determineworking voltage.

External Creepage The shortest distance along theoutside surface, between inputand output leads, measured inmm. Refer to Figure 4.

Dielectric Insulation VoltageWithstand Rating

The ability to withstand withoutbreakdown a 60 second appli-cation of a defined dielectricinsulation voltage between inputand output leads.

Distance Through Insulation

Distance between the photo-emitter and photodetectorinside optocoupler cavity (alsocalled internal clearance). Referto Figure 4.

Installation ClassI Equipment in closed

systems (e.g., telecom)

protected against over-voltage with devices such asdiverters, filters, capacitors,etc.

II Energy consuming equip-ment (e.g., appliances)supplied through a fixedinstallation.

III Primarily equipment in fixedinstallations (e.g., fixedindustrial equipment).

IV Primary supply level for

industrial factories.InsulationOperational - required forcorrect equipment operation butnot as a protection againstelectric shock.Basic - protects against electricshock.Supplementary - independentlyapplied to basic insulation toprotect against shock in theevent of its failure.Double - composed of bothbasic and supplementary.Reinforced - A single insulationsystem composed of severallayers (e.g., single andsupplementary).

Internal ClearanceSee Distance ThroughInsulation.


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Internal Creepage The shortest border distancebetween two separate insulating

materials measured betweenemitter and detector.

Material Group (see Compara-tive Tracking Index)I 600 < CTIII 400 < CTI < 600IIIa 175 < CTI < 400IIIb 100 < CTI < 175

Partial DischargeElectric discharge that partiallybridges the insulation betweentwo electrodes. Hewlett-Packard

supports partial dischargemeasurements per VDE0884, atechnique developed to evaluatethe integrity of insulatingmaterials. VDE’s philosophy isthat partial discharge testing

offers advantages over DielectricWithstand Voltage testing,which might adversely affect the

insulating material, and overthrough insulation distancerequirements which not onlyincrease manufacturing costsbut also do not necessarilyresult in acceptable insulatingcapability.

Pollution Degree1 - Nonconductive pollution

only.2 - Only occasional, temporary

conductivity due tocondensation.

3 - Frequent conductive pollu-tion due to condensation.

4 - Persistent conductive pollu-tion due to dust, rain orsnow.

Rated Mains VoltagePrimary power voltage declaredby manufacturer. Used to

categorize optocouplermaximum allowable workingvoltage.

For an in depth discussion onregulatory design requirementsand device specifications, pleaserefer to Hewlett-Packard’sOptoelectronics Designer’sCatalog.


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Common-Mode Transient Rejection

Circuit designers often encounter

the adverse effects of common-mode noise in a design. Once acommon-mode problem isidentified, there are several waysthat it can be resolved. However,common-mode interferencemanifests itself in many ways;therefore, it may be hard todetermine whether it is the causeof a circuit’s misbehavior. If asystem is connected and runningbut only produces erroneousdata, common-mode noise maybe the reason. This sectiondescribes sources of common-mode problems, presents possiblesolutions, and highlights thetechnology that Hewlett-PackardComponents Group uses toproduce opto-isolators withsuperior Common-ModePerformance.

Common-mode rejection (CMR)is a measure of the ability of a

device to tolerate common-mode

proprietary, low-cost Faraday

shield which decouples theoptocoupler input side from theoutput side. The second methodis by unique package designwhich minimizes input-to-outputcapacitance. The importance of these two strengths is explainedas follows.

Figure 5 illustrates a Common-mode transient pulse (VCM).

Figure 6a and 6b show interfer-ence circuit models for two typesof possible common-mode failuremechanisms for a single-transistor optocoupler. Thedashed lines are shown toindicate external componentsadded to the optocoupler. VCMrepresents a voltage spike acrossthe optocoupler isolation pathbetween the output-side ground(VG2) and input-side ground (VG1).VDM represents a signal voltage

applied across the input side.

noise. Hewlett-Packard specifies

common-mode rejection ascommon-mode transientrejection (CMTR ). CMTRdescribes the maximum tolerablerate-of-rise (or fall) of a common-mode voltage (given in volts permicrosecond). The specificationfor CMTR also includes theamplitude of the common-modevoltage (VCM) that can betolerated. Common-modeinterference that exceeds themaximum specification might

result in abnormal voltagetransitions or excessive noise onthe output signal. (CMTR isslightly different than common-mode rejection ratio CMRR ,often used for analog devices andcommonly specified in dB as theratio of the differential-mode gainto the common-mode gain.)

HP optocouplers rely on two keytechnical strengths to achieve

high CMTR. The first is use of a

Figure 5. Illustration of V CM Common-Mode Pulse.

Figure 6a. Interference CircuitModel.


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Figure 6b. Interference Circuit Model.

Referring to Figure 6a the para-sitic distributed capacitance CIS,which might tend to couple

transient current into the transistorbase node (for example when thetransistor is in the “off” state)terminates on an internal Faradayshield. Therefore the transientcurrent, ICM, gets diverted tooutput ground (VG2). Referring toFigure 6b, the parasitic distrib-uted capacitances, CIA and CIC areshown across the LED anode-to-ground (VG2) and LED cathode-to-ground (VG2) respectively.Because the LED anode is at a

relatively higher impedance thanthe cathode (i.e., RLED to ground)current at this point will tend tobe modulated slightly during CMtransients. For instance, if theLED is on, then during a positivetransient (i.e., dVCM/dt >0)current will be diverted awayfrom the LED. For fast enoughtransients, this may turn the LEDoff. (If RLED is connected to theLED cathode side then CICprovides a parasitic path to divertcurrent towards or away from theLED.) This type of failure isavoided by ensuring that CIA andCIC are small.

Figure 7 shows the possibleeffect on the output voltage levelof an optocoupler due to acommon-mode pulse. The output

is shown (successively) in thehigh and low states. (This mightbe observed if Rled were con-nected as in Figures 6a, 6b.)

Figure 7. Common Mode Interference Effect.


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Figure 8. Full-Bridge Power Switch Configuration.

ISOLATION

CONTROL

CIRCUITRY

GATE

DRIVE

GATE

DRIVE

GATE

DRIVE

ISOLATION

A1 B1

A2B2

MOTOR

HV+

GATE

DRIVE

HV -

12

transistors (A1,B1) is attached tothe drain of a second set of transistors (A2,B2). Whentransistor set A turns on, set Bturns off. Current flows from thepositive supply, through

transistor A1, through the load,and through transistor A2. Whenset B turns on, set A turns off,and the polarity of the currentthrough the inductive load isreversed.

How does this operation create acommon-mode problem? Theinput of each gate drive circuitryis referenced to the ground of thedigital control circuitry; theoutput common, on the otherhand, is floating and referencedto the source of its associatedpower transistor. The floatingcommons of the upper gate drivecircuits rapidly switch betweenthe positive and negative powersupplies. This rapid switchingcreates a large voltage swingacross the input to output of thegate drive circuitry. As an

As long as the amplitude VCM andvalue of dVCM/dt are less than theratings for the optocoupler beingused, VOH will remain above 2V(maximum TTL VIH) and VOL willremain below 0.8V (minimum

TTL VIL). Note that the slightperturbations in output voltageoccur sometime after the inputpulse which causes them, due tothe non-zero response time of theoutput transistor to the“perturbation signal.”

Common-mode signals canoriginate from several differentsources. A full bridge powerinverter, shown in Figure 8, is agood example of an applicationthat can exhibit large amounts of common-mode noise. Full-bridgeinverters are commonly found inmotor-speed control and switchingpower supply applications. Thepower inverter is generally usedto produce an ac output from adc input. In a full-bridge inverterapplication like that shown inFigure 8, the source of one set of

example, a half bridge circuit thatswitches between +250V and-250V in 100ns creates acommon-mode transient signal of 5000V/µs with an amplitude of 500V (see Figure 9). The device

that carries the control infor-mation to each MOSFET must beable to withstand this level of common-mode interference.Although this example may seemextreme, it is a fact that engineerscontinue to use faster-switchingtransistors to increase motorefficiency. Power MOSFETs, forexample, are commonly used inpower inverter applicationsbecause they are capable of highfrequency, high power switching.

The fast switching speeds of thetransistors, however, cangenerate common-mode signalswith very high rates of change(dVCM/dt).

The common-mode signal rate of rise can also be affected by thereverse recovery characteristicsof diodes D1 and D2 in the power


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MOTOR

+250 V

Q1

D1

-250 V

+250 V

∆V

∆t

500 V

0.1 s

5000 V

s= =

V = 500 VCM

dV

dt

V

s= 5000

CM

-250 V

100 ns

V CM

Q2

D2

V CM

Figure 9. Half-Bridge Example.

VCM

VCM

ID2

ID2

IQ1

Figure 10. Half-Bridge InverterWaveforms.

effective solution for common-mode problems, providingprotection against common-modetransients with slew rates as fastas 15 kV/µs at VCM as high as1500V.

High electrical noise levels canalso contribute to common-modeproblems. A significant amount of

electrical noise is found inindustrial environments as aresult of the starting and operatingof electric motors. When a largemotor first turns on, it normallyrequires a large in-rush current toreach operating speed. This largecurrent spike can generate asignificant amount of electricalnoise in its own and nearbysystems. Even the electric motorsin a typical household environ-ment vary in size from fractional

to low integral horsepower unitsand are often noisy ac-operatedor brushed dc-motors. Othersources of electrical noise includemicrowave ovens, weldingequipment, and automobileignitions.

Common-mode noise can enter asystem through conductive,inductive, or capacitive coupling.An example of a “conducted”

recovers from forward conduc-tion. The voltage and currentwaveforms shown in Figure 10illustrate what happens when Q1turns back on. As Q1 starts toturn on, the current through D2begins to decrease. The currentthrough D2 continues to decreaseand actually goes negative for ashort time due to the storage of minority carrier charge in its

junction. It is when this chargehas been depleted that D2 begins

to turn off and VCM begins toincrease. If D2 turns off veryquickly, VCM can also rise veryquickly, generating a largecommon-mode transient signal.

For the particular case of drivingthe gate of an IGBT or powerMOSFET in a power inverter, theHCPL-3120 IGBT/MOSFET gatedrive optical isolator is an

inverter shown in Figure 9; thesediodes are often referred to as“freewheeling” diodes. If theinverter is driving an inductiveload, such as a motor winding,these diodes may become forwardbiased during the normaloperation of the inverter. Forexample, assume that Q1 of Figure 9 is turned on, Q2 is off,and current is flowing throughQ1 and into the inductive load.When Q1 turns off, voltage VCMswings in the negative directionuntil diode D2 becomes forwardbiased and conducts the loadcurrent.

It is when Q1 turns back on thatvery high rates of rise can begenerated. In extreme cases,when Q1 turns on again, the rateof rise of voltage VCM is deter-mined by how quickly diode D2


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Figure 11. AC Equivalent Circuit for HCPL-261X.

noise voltage is the difference inground potential that may existbetween two connected systems

in a plant. The two systems mayexperience a small voltagedifference between their groundreferences. This voltage differencemight cause a ground-loopcurrent to flow. If the impedanceof the path through which theground-loop current flows is largeenough, a significant amount of interference will result. Capaci-tive or inductive coupling mayoccur when signal wires run closeto ac power cables. Electromag-

netically induced interference(EMI) can also be coupled fromadjacent signal lines or nearbyequipment, especially in factoryenvironments. Other sources of common-mode noise that can becoupled into a system includelightning strikes and electrostaticdischarge (ESD).

Optical isolation is a useful tech-nique for reducing common-modeinterference. Optocouplers, liketransformers and capacitively-coupled devices, provide isolationbetween the input and output of asystem. Transformers, by virtueof their high primary-to-secondary capacitance, tend tohave lower CMTR capability.Capacitively-coupled devices tendto have poor CMTR capability(since in these devices fast,transient common-mode pulsespass across the coupling capaci-

tor and are not filtered out.)Optocouplers, having low input-

to-output capacitance, typicallyprovide better common-moderejection than transformers orcapacitively-coupled devices. TheCMR specification of anoptocoupler ranges up toVCM =1500V amplitude and upto 15,000V/µs rate of change of VCM, for high-CMR products.

Another advantage of optocoup-lers lies in the area of EMIgeneration and susceptibility.

Transformers typically radiateelectromagnetic interference(EMI) and are susceptible tomagnetic fields. Capacitively-coupled devices generate ground-loop current, thus generatingEMI. Optocouplers use light fordata transmission; additionally,they effectively eliminate ground-loop current. Therefore, they donot radiate nor are they affected

by stray magnetic fields. Thisability is well-recognized in the

European Community wheresystems designers need toachieve system-level standards(now adopted as EN50081/EN50082 which set limits on theamount of acceptable EMI asystem radiates or to which it isimmune.)

A technique which may be usedto further enhance CMTR is an“LED split-resistor” technique asshown in Figure 11; (note thatthe VDM which would appearbetween the top and bottomRLEDs has not been shown in this“ac equivalent circuit”). By usingtwo LED-resistors (instead of one) the current change at theanode of the LED is nearlycanceled by the current change atthe cathode, thus tending to keepthe LED current constant. Thismakes the optical isolator more

immune to CM transients whereCLA and CLC limit CMTR.


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LED Degradation over Time

One concern for optocoupler

lifetime is that LED light-output(LOP) decreases over time.Generally, light-output degrada-tion gets worse with increasingoperating temperature andoperating LED current. A worst-case scenario is that over time, asthe LED becomes dimmer, theLOP will fall below the minimumvalue needed for a part to switchproperly. Hewlett-Packard, anindustry leader in LED technol-ogy, tests LOP degradation under

accelerated conditions in order toprovide designers with informa-tion on the expected operatinglifetime of optocouplers.Optocouplers which have aninput driver IC are designed suchthat the driver IC sets the properinput IF, guardbanding forexpected LED LOP degradationover the life of the optocoupler.(Examples are the HCPL-3700,HCPL-7101, and HCPL-7820.)On the other hand, optocouplers

requiring an input current-settingresistor (i.e., without an inputdriver IC) require that the circuitdesigner guardband the minimum

recommended operating IF by an

amount sufficient to account forexpected LOP degradation.

Hewlett-Packard has undertakentesting of LED degradation forperiods of continuous operationup to at least 10 khours forvarious LEDs used in Hewlett-Packard optocouplers. Figures12a and 12b show the normalizedlight output over a 10,000 hourperiod for Gallium ArsenidePhosphide (GaAsP) and

Aluminum Gallium Arsenide(AlGaAs) LEDs respectively.

Figure 13 shows LOP as afunction of IF for a GaAsP LEDunder operating conditions of IF =20mA at an ambienttemperature of TA =125°C.Curves are shown for t =0 hoursand t =10 khours of continuousoperation.

Optocouplers which use theGaAsP and AlGaAs LEDs arelisted in Figures 12a and 12b.

Figure 14 illustrates how, based

on knowledge of initial and post-stress LOP vs. IF, (for a GaAsPLED) a minimum guardbanded IFcan be determined to provide forLOP degradation over the life of the LED. For this case, theminimum recommended IF att =0 hours (IF(min)) of 5mA isguardbanded for 10khours of operation to a value of 6.1mA.

Note that in Figure 14 if the LOPvs. IF curves were linear over the

range between IF(min) and IGB(min)(minimum IF guardbanded fort =10khours) then the amountof guardbanding (percentchange) would be equal to theamount of LOP degradation(percent change). Since in ourcase the curve is “concave up”the amount of guardbanding isslightly less than the percentchange in LOP between t =0 andt =10 khours. Figure 15 (whichis a plot of the slope of the(t =0) curve in Figure 14),shows that the slope is increasingup to about IF =20 mA, at which


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Figure 13. Typical GaAsP LED Light-Output (LOP) vs. I F After 0 khours and 10khours of Continuous Operation at 125°C, I F = 20 mA.

point it flattens out and beginsdecreasing.

By empirically modeling thetypical GaAsP LOP vs. IF curveand applying knowledge of worst-case (-3σ) degradation overtime, guardbanded IGB(min) for atypical LED can be reduced to thefollowing equation:

I F(min) I GB(min) = ––––––1

–a δ

≈ I F(min) × 1.214

where,

I F (min) = minimum recom-mended IF at t = 0 hours.

I GB (min) = minmum guardbandedIF after t = 10 khours.

a = 1.3 (empirical curve - fit)

δ = Post-stress LOP Factor(≈ 0.784 for 10 khours,

TA =125°C, I F = 20 mA )

This equation applies well whenIF is approximately constant.

Example: To calculate the

appropriat e I GB(min) for an

HCPL-3120 not e that

I F(min) = 7 mA. Applying the

above relationship for 10 khou r

guardbanding,

I GB(min) = 8.50 mA.

Figure 12a. Normalized LED Light Output (LOP) vs. Time for GaAsP LED(Stress I F = 20 mA, T A = 125°C).

Figure 12b. Normalized LED Light Output (LOP) vs. Time for AlGaAs LED(Stress I F = 25 mA, T A = 125°C).


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Figure 15. Slope of Typical GaAsPLOP vs. I F.

Figure 14. GaAsP LED Light Output (LOP) vs. I F on a Linear Scale (Stressed atTA =125°C, T F =20mA).

Factors which will increaseexpected LED guardbanded-operation times are:1. Operation at lower I F: LOP

decreases less with reducedoperating IF. Therefore, opera-tion at IGB


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ESD Precautions: Standardelectrostatic discharge precau-tions should be taken in handlingand assembly of the optocouplersto prevent damage or degradationof the device.

Printed Circuit Board Layout:

An optocoupler performs reliablyonly in a correctly designedcircuit. In most digital optocoup-lers the amplifier at the output isrequired to operate with the very

low photocurrent from thephotodetector. Consequentlythese amplifiers can be sensitiveto electrical disturbances. It istherefore necessary to haveproper shielding and bypassing of the VCC and Ground traces.Bypassing closely to each of theoptocouplers VCC-to-Ground pinswith low-inductance ceramiccapacitor is recommended asshown in Figure 17.

Figure 17 shows an optional PCBlayout for a high speed digitaloptocoupler for improvingelectrical noise immunity. Theoptional VCC and Ground tracesbetween the pin rows of theoptocoupler help shield theoutput circuitry from electricaldisturbances on the input pins,thus improving common-moderejection.

Guidelines for Printed Circuit Board Assemblyand Layout

HP optocouplers are suitable forautomatic printed circuit board(PCB) assembly operationsincluding surface mount assembly.

The following guidelines arerecommended for proper opera-tion and long term reliability of

HP optocouplers.

Solder Reflow Process: Only onesoldering operation is recom-mended within the thermal profileshown in Figure 16. With infraredlamp heating, use precautions toavoid localized temperature risein the resin. Also, the resinshould not be immersed in the

Figure 16. Maximum Solder Reflow Thermal Profile.

solder. To prevent chloridecorrosion of the lead frame,halide fluxes should not be used.

Wave Soldering: The maximumsolder temperature allowed is260°C for 10 seconds, with the

solder 1.6 mm below the seatingplane.

Solvent Cleaning: The solventtemperature and immersion timeshould not exceed 45°C and threeminutes respectively. For ultra-sonic cleaning, environmentallysafe solvents such as ethyl andmethyl alcohol are recommended.

Figure 17. Optional Printed Circuit Board Layout for Improved Electrical Noise Immunity.


18/7027

Digital Logic Interface/LevelShifting Applications

Description The circuit shown is an interface

between two TTL gates using anactive output (totem pole) opto-coupler, the HCPL-2201. A seriesswitching circuit drives theoptocoupler LED. The designerchooses RIN to agree with theequation shown in the schematic.

The active output of the HCPL-2201 can be directly connectedto a TTL gate, and no pull-upresistor is required. The HCPL-2201 can sink enough current tohandle up to 16 LSTTL or 4 TTLloads.

Performance of Circuit• Maximum optocoupler propa-

gation delay: 300 ns (refer toalternative HP parts for lowerpropagation delay times)

• Typical signaling rate: dc to 5MBd (refer to alternative HPparts for higher speeds)

• Typical optocoupler LED drivecurrent: 2 mA

Benefits• No pull-up resistor required on

the optocoupler output

interface• Low power dissipation on the

optocoupler input circuit

• Up to 20 V supply voltage forthe HCPL-2201

ReferencesHCPL-2201 Logic Gate

Optocoupler Technical Data

Alternative HP Parts1) HCPL-07XX, HCPL-2730/1,

HCPL-4701, 6N138/9,CNW138/9 Low Input CurrentOptocouplers

2) HCPL-0201/11 Small-OutlineLogic-Gate Optocoupler

3) HCPL-52XX Hermetic Logic-Gate Optocoupler

4) CNW2201/11 Widebody Logic-

Gate Optocoupler5) HCPL-7101 50 MBd CMOS

Logic-Gate Optocoupler

6) HCPL-2230/1 Dual-ChannelLogic-Gate Optocoupler

7) HCPL-05XX, HCPL-2530/1,HCNW135/6, 6N135/6 HighSpeed Optocoupler

TTL Interface with Series LED Drive


19/7028

Description The above circuit shows how a0to 5 V logic signal can be levelshifted to a -15 to 0 V signal. Thecircuit can safely be used forlevel shifting up to ±800 V. Thecircuit uses an open collectoroutput logic gate, the 74LS405,to drive the LED of the HCPL-4502/3 optocoupler. The HCPL-4502/3 also has an open-collectoroutput. The designer chooses RINto agree with the equation shownin the schematic. This equationsets the value of the optocouplerLED forward current. The outputof the HCPL-4502/3 requires a

pull-up resistor, RL. The current-transfer ratio (CTR) of the opto-coupler determines the maximumamount of current the optocoupleroutput can sink while maintainingthe output voltage (between pins5 and 6) of 0.5 V or less.

Performance of Circuit• Maximum optocoupler

propagation delay: 2 µs (referto alternative HP parts forlower propagation delays)

• Typical signaling rate: dc to 1MBd (refer to alternative HPparts for higher speeds)

• Typical optocoupler LED drivecurrent: 10 to 16 mA

• Maximum output supplyvoltage (pins 8-5): 30 V

• Minimum CMR: 15 kV/µs slewrate, 1500 V peak

Benefits

• Reduces transient immunityproblems

• Convenient way of replacingpulse transformer for high-voltage level shifting

ReferencesHCPL-4502/3 High SpeedOptocoupler Technical Data

Alternative HP Parts1) HCPL-07XX, HCPL-2730/1,HCPL-4701, 6N138/9,HCNW138/9 Low InputCurrent Optocouplers

2) HCPL-55XX Hermetic HighSpeed Optocoupler

3) HCPL-7101 50 MBd CMOSLogic Gate Optocoupler

4) HCPL-0710 SO-8 High SpeedCMOS Optocoupler

Level Shifting/TTL Interface with ShuntLED Drive


20/7029

Performance of Circuit• Minimum optocoupler LED

turn-on current: 0.5 mA (TheHCPL-4701 optocouplerrequires only 40 µA)

• Typical signaling rate: dc to100 kBd

• Minimum optocoupler currenttransfer ratio: 400%

Benefits• Low power consumption

• Simple interface

ReferencesHCPL-0700/11 High GainOptocoupler Technical Data

Alternative HP Parts1) HCPL-4701 Very Low PowerHigh Gain Optocoupler

2) HCPL-2730/1 Dual ChannelHigh Gain Optocoupler

3) HCPL-0731 Small Outline HighGain Optocoupler

4) HCPL-57XX, HCPL-67XX,6N140 Hermetic High GainOptocoupler

DescriptionA CMOS-to-CMOS interface ispossible with HP optocouplers.

The above circuit shows a cost-effective interface for 100 kBdapplications. The 74HCT04CMOS Hex Inverter that drivesthe optocoupler LED can sourceand sink up to 4 mA current. The6N139 optocoupler requires only0.5 mA LED current foroperation. The signal diodeacross resistor R1 protects againstcommon-mode transient voltagesand is optional. The outputcircuit uses a 74HCT08 so thatthe signal from VIN to VOUT is not

inverted.

Low Power 100 kBd CMOSInterface


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22/7031

DescriptionUp to 50 MBd CMOS-to-CMOSinterface is possible with theHCPL-7100 optocouplers. Theabove circuit requires only abypass capacitor on each of theHCPL-7101 input-side andoutput-side power supply pins.

Performance of Circuit• Typical logic high input power

supply current for HCPL-7101:10 mA

• Typical logic high output powersupply current for HCPL-7101:9 mA

• Typical HCPL-7101 signalingrate: dc to 50 MBd

• Typical HCPL-7101 pulse-widthdistortion: 2 ns

• Typical HCPL-7101 propaga-tion delay: 28 ns

Benefits• Low power consumption

• Very simple interface

ReferencesHCPL-7100/1 High Speed CMOSOptocoupler Technical Data

Alternative HP PartsHCPL-2300: 8 MBd Low InputCurrent Optocoupler

HCPL-0710: SO-8 High SpeedCMOS Optocoupler

50 MBd CMOS Interface


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24/7033

Description The above schematic shows avery simple RS-232C datacommunication isolation interfaceusing a 6N139 optocoupler. Thiscircuit operates with an LEDforward current of 0.5 mA whenthe input is at 3 V. The 1N4150diode protects the LED duringnegative signal voltages. Since alow diode current is used tooperate the 6N139, the twistedpair line can be up to 120 m.However, the data rate may haveto be lowered to account forslower charging and dischargingof the total line capacitance.

Performance of Circuit• RS-232C link twisted pair cable

length: up to 120 m for lowdata rates

• Typical optocoupler propaga-tion delay: 20 µs

Benefits• Simple, low cost isolated

interface

References6N139: High-Gain, Low InputCurrent Optocoupler

Alternative HP Parts1) HCPL4701, 6N138/9, 4N45/6,HCPL-2730/1 High-Gain, LowInput Current Optocoupler

2) HCPL-0700/1, HCPL-0730/1,Small Outline High-Gain, LowInput Current Optocoupler

Data CommunicationsApplications

Isolated RS-232C Interface


25/7034

Description The above isolated RS-422 circuituses two high-speed optocouplersthat can switch up to 10 MBdsignals. An isolated power supply(VCC2) is required to power theDS75176A driver/receiverintegrated circuit.

Performance of Circuit• Typical signaling rate: up to 10

MBd

• Optocoupler LED drive current:5 mA

• Typical Optocoupler TransientRejection: 10,000 V/µs slewrate, 50 V peak (highertransient rejection withHCPL-2611)

Benefits• Compact design with small

outline optocouplers

• Prevents common-modetransients from interfering withthe signal

ReferencesHCPL-0601 Small Outline HighSpeed Optocoupler TechnicalData

Alternative HP Parts1) HCPL-0611 High-CMR, Small

Outline High SpeedOptocoupler

2) HCPL-2611 High Speed, HighCMR Optocoupler

3) HCNW2601/11 WidebodyHigh Speed Optocoupler

4) HCPL-5601 Hermetic HighSpeed Optocoupler

Isolated RS-422Interface


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27/7036

DescriptionDeviceNet, a factory floor com-munication network standard,sometimes may require connect-ing devices to be electricallyisolated. The HCPL-7101, highspeed CMOS optocoupler with a40 ns maximum propagationdelay time meets the DeviceNetPhysical layer specification.

Performance of Optocoupler• Signaling rate: up to 50 MBd

• Typical propagation delay: 28 ns

• Typical pulse-width distortion:2 ns

Benefits• Fast data access time or latency

• Elimination of transients resultsin high data integrity

• Meets worldwide isolation safetystandards: UL, CSA, VDE

References1) HCPL-7101 High Speed

optocoupler Technical Data

2) DeviceNet Specification, AllenBradley Company

Alternative HP Part

HCPL-0710 SO-8 High SpeedCMOS Optocoupler

Isolated DeviceNet/CANInterface


28/7037

Description The above half-duplex, point-to-point, multi-drop, 20 mA currentloop configuration can alternat-ingly transmit bi-directional dataover two wires. Only one currentsource is required. Each isolatedstation with an HCPL-4100transmitter and HCPL-4200

receiver optocouplers providesexcellent common-moderejection.

Performance of Circuit• 1 mA noise margin in the

“space” state

• 8 mA noise margin in the“mark” state

• Typical signal rate anddistance: 40 m at 100 kBd;over 200 m at 10 kBd

Benefits• Maintains data integrity

• Simple data transmissionsystem for industrialapplications

References1) HCPL-4100/4200 20 mA

Current Loop Optocoupler Technical Data

2) Application Note AN1018,“Designing with the HCPL-4100 and 4200 Current LoopOptocoupler”

HCPL-4100 TRANSMITTER HCPL-4100 RECEIVER

Isolated 20 mA Current LoopInterface


29/7038

Description The above differentially drivencircuit can use up to eight 6N138optocouplers at various receiversalong the 90 m line. All stationsare isolated. The first stationwould draw approximately2.7mA current, and the laststation 1.8 mA of LED drivecurrent. The output grounds of the optocoupler may beelectrically separate.

Performance of Circuit• Typical signaling rate: 18 kBd

(faster signaling rates can beobtained with HCNW139 and

6N139)• Typical optocoupler propaga-

tion delay time: tPHL = 2 µs;tPLH = 20 µs

• Up to 90 m distance

Benefits• Simple, low-cost, multidrop

circuit for low signaling rates

References6N138/9 Low-Input CurrentOptocoupler Technical Data

Alternative HP Parts1) HCPL-0700/01/30/31, HCPL-M700/1, HCNW138/9, andHCPL-2730/31 Low-InputCurrent Optocouplers

2) HCPL-57XX, HCPL-67XX, and6N140 Hermetic Low-InputCurrent Optocouplers

3) HCPL-2300 High Speed, LowInput Current Optocoupler

Multidrop LineReceiver


30/7039

Isolated Balanced LineReceiver - Circuit No. 1

DescriptionA balanced RS-422 line driverdifferentially drives a twisted pairline. Two HCPL-2300s providebalanced signal direction for thisline. The thresholds of the HCPL-2300 will be nearly equal, provid-ing symmetrical signal detectionlevel. Since the propagationdelays of the two optocouplersare similar, the pulse-widthdistortion for this scheme will bequite low for considerable linelengths. The Exclusive-Or flip-flop circuit at the optocoupleroutput increases CMR protectionto an extremely high level andbalances the propagation delays.For less demanding noiseenvironments, only one HCPL-2300 with no EX-OR flip-flopmay be used. The maximum datarate, however, will be somewhat

lower.

Performance of Circuit• Signaling rate: > 10 MBd at

100 m line length

• Common mode rejection:>15,000 V/µs

Benefits• Very high common-mode

transient rejection

• Data transmission for up to

1km distance

References1) HCPL-2300 Low-Input Current

High Speed Optocoupler

2) AN 947: Digital Data Transmis-sion Using Optically-CouplerIsolators

Alternative HP PartsHCPL-2602/12 High CMR LineReceiver


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32/7041

Description The above circuit converts asingle-ended signal to a split-phase signal with a 75159 Tri-State Line Driver and dual-channel HCPL-4661 High CMROptocoupler. When Input Enablegoes low, the lower channel of the optocoupler operates the“strobe” input of the 75159 tomake both outputs open.

Performance of Circuit• Optocoupler signaling rate: up

to 10 MBd

• Optocoupler CMR: 15,000 V/µs

at 1000 V peak (typical)

Benefits• Higher data rate than a current

source pull-up

• High CMR performance reducesor eliminates transient noise

ReferencesHCPL-4661 Dual Channel HighCMR Optocoupler Technical Data

Alternative HP Parts1) HCPL-063N SO-8 High CMRDual Channel Optocoupler

2) HCPL-2631 Dual Channel HighSpeed Optocoupler

3) HCPL-0631 Small Outline, DualChannel Optocoupler

4) HCPL-56XX Hermetic HighSpeed Optocouplers

Isolated Tri-State LineDriver


33/7042

Description The above illustration is anunbalanced line receiver usingthe integrated voltage-clampinput optocoupler, HCPL-2602.

The circuit is unbalanced becausethe termination impedance isdifferent for both “ends” of thedifferential signal received by theHCPL-2602. TTL data is con-verted to a differential signal viathe differential line driver 9614,and transmitted over twisted-pairwire. The Schottky diode helps toimprove the turn-on and turn-off delays.

Performance of Circuit• Signaling rate: up to 2 MBd at

90 m (up to 10 MBd withpolarity non-reversing driver)

• Optocoupler common-modetransient rejection:10,000 V/µs (typical)

Benefits• Integrated line termination and

voltage clamping saves boardspace

• Differential driver and opticalisolated receiver reduce oreliminate transient noiseinterference

ReferencesHCPL-2602/12 High CMR LineReceiver Optocoupler

Alternative HP Parts1) HCPL-2611 High CMR, HighSpeed Optocoupler

2) HCPL-0601/0631 Small Outline,High Speed Optocoupler

3) HCNW2601 Widebody, HighSpeed Optocoupler

Isolated Unbalanced LineReceiver


34/7043

Peformance of

HCPL-0710 Optocoupler• Pulse Width Distortion 8ns max 10 kV/µs

• Minimium Common Mode Rejection• 5V CMOS Compatibility

Benefits• Fast access time or latency• High CMR performance increases system reliability• HCMOS/CMOS capatible inputs simplifies overall solution

Description The Profibus DP 12Mbcommunication standard physicallayer specification, requires that

all devices be galvanicallyisolated.Hewlett Packards HCPL-0710 andHCPL-7101 meets the isolationrequirements. The circuit requiresan isolated power supply for theoptocoupler outputs and the linedriver/reciever.

References1) HCPl-0710 Technical Data2) HCPL-063N Technical Data

Alternative HP PartHCPl-7101

Profibus DP 12 MBd Interface


35/7044

Description The 6N139 Low-Input CurrentOptocoupler is used to detectstandard telephone ring signals.At the optocoupler output, a0.1µF base-collector capacitorprovides a large enough Miller-capacitance so that a low-frequency ring signal (20 to60Hz) causes the output toremain low when ringing occurs.

Performance of Circuit• Can detect 20 to 60 Hz, 30 to 80

VRMS telephone ring signals

Benefits• Simple and inexpensive circuit

for ring signal detection

• Meets worldwide regulatoryisolation standards

References6N139 Low-Input CurrentOptocoupler Technical Data

Alternative HP Parts1) HCPL-0701 Small Outline, Low-

Input Current Optocoupler

2) HCPL-3700/60 ThresholdSensing Optocoupler

3) HCNW139 Low-Input CurrentOptocoupler

Telephone Ring Detection

TelecommunicationsApplications


36/7045

Description The HCPL-4701 Low PowerOptocoupler is suitable forstandard telephone line interfacefunctions such as: ring detection,line polarity, and power on/off detection. Integrated ServicesDigital Network (ISDN) applica-tions severely restrict the inputpower that an optocouplerinterface circuit can use, whichmakes the HCPL-4701 an idealchoice.

Performance of Optocoupler• Input current for turn-on: 40µA

• Typical total power dissipation

with IF = 40 µA: < 3 mW• Typical propagation delay:

65µs

Benefits• Low power dissipation

• Compatible with 3 V Logic

ReferencesHCPL-4701 Lower PowerOptocoupler Technical Data

ISDN Interface


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38/70


39/7048

Description The HCPL-7800/7820 IsolationAmplifiers can be used forisolating the motor currentsensing element from the controlcircuit while at the same timetransmitting precision analogsignals. This circuit requires ahigh precision sensing resistorfor monitoring the motor current.

The voltage across the sensingresistor is fed to the HCPL-7800/

7820 input pins 2 and 3. Thesensing resistor is available fromseveral suppliers, which are listedin the reference section below.

References1) HCPL-7820 Technical Data

2) HP Application Note 1078,Isolation Amplifier design andapplications

3) High precision current sensingresistor suppliers: Dale inUSA; Isabellenhutte inGermany; and PCN in J apan

Alternative HP Part

CNR200/1 - General purposeanalog optocoupler for buildingisolation amplifiers

Motor Control Applications

Motor Current Sensor/IntegratedIsolation Amplifier

Performance of Circuit• Can sense current up to 200 A

or more

• Optocoupler bandwidth: Up to200 kHz (HCPL-7820)

• Optocoupler nonlinearity:0.05% (HCPL-7820)

• Optocoupler input offsetvoltage: 0.9 mV (typical)

• Optocoupler common-moderejection:15 kV/µs

Benefits• Small size and lower profile

circuit compared to Hall-Effectdevice based current sensingcircuits

• Easy availability of componentsrequired in this circuit

• High precision measurementwhile at the same timemaintaining transient immunity


40/7049

Isolated Gate Driver for IGBT/MOSFET -Circuit No. 1

Description The HCPL-4503/4 providesisolation for the controller thatdrives the power components(MOSFETs or IGBTs). The circuitprovides full regulatory-approvedisolation between the power andcontrol circuits. The HCPL-4503/4 optocouplers can rejecttransients that have very highslew rates while at the same timetransmit signals without muchpropagation delay.

Performance of Optocoupler• Minimum 15 kV/µs transient

immunity

• Typical propagation delay lessthan 1 µs

• Propagation delay differencebetween any two HCPL-4504optocouplers: 0.9 µs or less

Benefits• Avoids dangerous false turn-on

in industrial environments

• Reduced total harmonic distor-tion for inverter ac output

• Reduced “Dead Time” for

power transistor switching

References1) Application Brief 100, “HP

Optocouplers for MotorolaPower Module Interface”

2) HCPL-4503/4504 TechnicalData

Alternative HP Parts1) HCNW4503/4504 Widebody

High-CMR Optocoupler

2) HCPL-0453/4 Small-OutlineHigh-CMR Optocoupler

3) HCPL-3100/1 Gate DriveOptocoupler

4) HCPL-4506/0466 Gate DriveInterface Optocoupler

5) HCPL-52XX Hermetic High-CMR Optocoupler


41/7050

Isolated Gate Driver for IGBT/MOSFET - Circuit No. 2

Description The HCPL-2211/2212 providesisolation for the controller thatdrives the power components(MOSFETs or IGBTs). Thiscircuit provides full regulatory-approved isolation between thepower and control circuits. TheHCPL-2211/12 optocouplers canreject transients that have veryhigh slew rates while at the sametime transmit signals withoutmuch propagation delay.

Performance of Optocoupler• Minimum 10 kV/µs transient

immunity

• Typical optocouplerpropagation delay: 150 ns

• CMOS drive circuit foroptocoupler LED input

Benefits• Avoids dangerous false turn-on

in industrial environments

• Reduced total harmonic distor-tion for inverter ac output

• Reduced “Dead Time” forpower transistor switching

References1) Application Brief 100, “HP

Optocouplers for MotorolaPower Module Interface”

2) HCPL-2211/12 Technical Data

Alternative HP Parts1) CNW2211 Widebody High-

CMR Optocoupler

2) HCPL-0211 Small-OutlineHigh-CMR Optocoupler

3) HCPL-3100/1 Gate DriveOptocoupler

4) HCPL-4503/4 High-CMROptocoupler

5) HCPL-4506/0466 Gate Drive

Interface Optocoupler6) HCPL-52XX Hermetic High-

CMR Optocoupler


42/7051

Isolated Gate Drive for IGBT/MOSFET- Circuit No.3

Description This circuit uses the HCPL-3120integrated base drive optocouplerfor driving IGBTs and MOSFETs

in a power inverter. The outputinterface for the HCPL-3120requires only a few passivecomponents for driving the baseof an IGBT/MOSFET.

Performance of Optocoupler• Gate drive current: 2.0 A peak,

• Guaranteed common-mode

transient immunity: 15,000 V/µs, at Vpeak = 1,500 V

• Under Voltage Lock-OutProtection (UVLO)

• 500 ns Maximum SwitchingSpeeds

• 0.5 V Maximum Low LevelOutput Voltage (VOL)

Benefits• Fewer components

• Low Level

Output Voltage (VOL)Can eliminate Need forNegative Gate Drive

ReferencesHCPL-3120 Technical Data

Alternative HP Parts1) HCPL-3101 Gate drive optocoupler

2) HCPL-3101 Gate drive optocoupler

3) HCPL-3150 Gate drive optocoupler


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44/7053

Isolated Base Drive for BipolarPower Transistors

Description The HCPL-3000 Base DriveOptocoupler is used to drivebipolar power transistors in anH-Bridge inverter circuit. The

HCPL-3000 contains anintegrated base driver circuit atits output, which eliminatesactive components that may beotherwise required.

Performance of Optocoupler• 1.0 A peak, 0.5 A continuous

base drive current capability tothe power transistor

• 1.5 kV/µs, 600 V peakcommon-mode transientimmunity

• 2 µs propagation delay

Benefits• Fewer components by

eliminating buffer stage

• Low propagation delay givescapability for higher carrierfrequency

• Cost-effective solution forconsumer appliances

References1) HCPL-3000 Technical Data

2) HP Application Note 1058,“Power Transistor Gate/BaseDrive Optocouplers”

Alternative HP PartHCPL-4506 High CMROptocoupler


45/7054

Isolated High-Voltage Sensor -Circuit No. 1

Description The HCPL-7820 isolationamplifier can be used for sensingthe rectified dc power supplyvoltage in a power inverter. Theresistor divider network is usedso that the full scale voltage atthe HCPL-7820 input is 200mV.An isolated 5 V power supply isrequired to power the HCPL-7820input circuit.

Performance of Optocoupler• 15 kV/µs transient rejection

• 0.05%nonlinearity

Benefits• Few components

• High electrical noise immunity


Alternative HP Part

HCPL-4562 Analog Optocoupler


46/7055

Description The HCPL-4562 LinearOptocoupler is used in a servocircuit to sense the rectified dcpower supply voltage of a powerinverter. The series resistor R1limits the current that drives theinput LED of optocoupler U1.When the circuit is balanced withthe potentiometer R3, the outputvoltage V0 is proportional to thehigh voltage dc power supply.

Performance of Optocoupler• 122 dB isolation mode rejection

ratio

• 0.25% nonlinearity

Benefits• Simple circuit

• No isolated 5 V input powersupply is required foroptocoupler U1


Alternative HP Parts

1) HCPL-7820 Isolation Amplifier2) HCNR200/1 AnalogOptocoupler

Isolated High-Voltage Sensor -Circuit No. 2


47/7056

Motor Control Isolated A/D

ReferencesHCPL-7860,HCPL-870/7870

Technical Data

Alternative HP PartHCPL-7820 Isolation Amplifier

Performance of Circuit• 15 kV/µS Isolation Transient Immunity• 12-bit Resolution• Less than 0.05%Non-linearity

• High-Speed Fault Detection Circuit• - 40°C to + 85°C Operating Temperature Range

Benefits• Lower overall solution cost• Auto insertable• Excellent offset and gain stability• Easy interfacing to uP

• Very high transient immunity

Description The need to isolate and digitallyprocess precision analoguesignals in a motor control circuit,can pose many challenges for the

designer. The circuit demonstrates the useof an A/D converter to isolateboth current sense signals andanalogue speed control inputs ina high noise enviroment.

This circuit which implementsHewlett-Packard’s Isolated A/Dconverter, delivers the completesolution and requiredperformance at significantlylower overall cost than

alternative solutions.


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49/7058

Precision Isolation Amplifier for UnipolarSignals

Description This circuit uses the HCNR200/1High-Linearity Analog Optocoup-ler to achieve high accuracy andwide dynamic range at a reason-able cost. This is accomplishedby using low-cost, precision op-amps with very low input biascurrents and offset voltages. Thecircuit couples only positivevoltage analog signals.

Performance of Circuit• DC to 10 kHz bandwidth

• Stable gain

• 0.1% nonlinearity

• 1 mV to 10 V input/outputvoltage range

Benefits• Low-cost, high-accuracy solu-

tion for coupling analog signals

• Easy availability of supportcircuit components

• No offset adjustment isrequired

ReferencesHCNR200/1 Technical Data


1) HCPL-7820 Isolation Amplifier2) HCPL-4562 Wideband Analog/

Video Optocoupler


50/7059

Isolation Amplifier for Bipolar Signals -Circuit No. 1

Description This circuit shows how theHCNR200 High Linearity Opto-coupler can be used for transmit-ting bipolar analog signals acrossan isolation boundary. Thiscircuit uses two optocouplers:OC1 and OC2; OC1 handles thepositive portions of the inputsignal and OC2 handles thenegative portions. Diodes D1 andD2 help reduce cross-over distor-tion by keeping both amplifiersactive during both positive andnegative portions of the inputsignal.

Performance of Circuit• 0.01% nonlinearity

• Bandwidth: dc to 100 Hz

• Low transfer gain variation:

±5% (K3 of HCNR201)

Benefits• Low drift

• Low crossover distortion withinthe dc to 100 Hz frequencyband

• Good linearity

• Very low offset


Alternative HP Part

HCPL-7820 Isolation Amplifier


51/7060

Isolation Amplifier for Bipolar Signals- Circuit No. 2

Description This circuit shows how bipolaranalog signals can be transmittedacross an isolation boundary byusing just one HCNR200 opto-coupler. This circuit provides aneasy interface to A/D converterswith two output signals: ananalog signal proportional to themagnitude of the input signal,and a digital signal correspondingto the Sign of the input signal.

The HCNW138 optocoupler,which couples the Sign signal,can be substituted with a fasteroptocoupler in case the Signchanges faster than 50 kHz.



1) HCPL-7820 Isolation Amplifier2) HCNW2601 High Speed DigitalOptocoupler (for the Signsignal)

Performance of Optocoupler• 0.01% nonlinearity

• Wide bandwidth: dc to 1 MHz

• Low transfer gain variation:±5% (K3 of HCNR201)

Benefits• Low drift

• Very low offset

HCNW138


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53/7062

AC-Coupled IsolationAmplifier

Description This circuit with the HCPL-4562Wideband Analog/VideoOptocoupler functions as an ac-coupled isolation amplifier thatcan be used for coupling audio orvideo signals. The input circuitbiases the optocoupler LED at aquiescent current of about 6 mA,determined primarily by resistorsR1, R2, and R3. Diode D1 helps tostabilize the operating point overthe operating temperature range.An ac-coupled signal will modu-late the collector current of transistor Q1 and the optocouplerLED. The output circuit consists

of a simple transresistance(current-in, voltage-out) amplifierfollowed by a common-emitteramplifier stage.

Performance of Circuit• Typical bandwidth: 13 MHz

• Nominal gain of circuit: 1

• Isolation-mode rejection: 46 dB

at 1 kHz• Overall nonlinearity: 0.5%

• Optocoupler input currentrange: 4 mA-8 mA

Benefits• Simple solution for coupling

audio and video signals

References1) HCPL-4562 Wideband Analog/

Video Optocoupler TechnicalData

2) Application Note 951-2,“Linear Applications of Optocouplers”

Alternative HP Parts1) HCPL-2502, 6N135, 6N136

High Speed Transistor Outputoptocouplers

2) HCNW4562 Widebody Wide-band Analog/Video Optocoupler

3) HCPL-55XX, 4N55, HCPL-6530/1 Hermetic High SpeedOptocoupler

4) HCPL-05XX Small-OutlineHigh Speed Optocoupler


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55/7064

Differential DC Isolation Amplifier

Description The above schematic uses a dual-channel, high-speed optocoupler(HCPL-2530/1) to function as adifferential dc isolation amplifier.

This circuit operates on theprinciple that an operating regionexists where a gain increment of one optocoupler can be approxi-mately balanced by the gaindecrement of a secondoptocoupler.

Performance of Circuit• 3%nonlinearity for 10 V peak-

to-peak dynamic range

• Gain drift: -0.4%/°C

• Offset drift: ±4 mV/°C• 25 kHz bandwidth (limited by

Op-Amps U1, U2, U3, and U4)

Benefits• Simple coupling circuit for dif-

ferential input analog signals

References1) HCPL-2530/1 Dual Channel

High Speed Optocoupler Technical Data


Alternative HP Parts1) HCPL-0530/1 Small-Outline

Dual Channel High SpeedOptocoupler

2) HCPL-5530/1, HCPL-6530/1Hermetic Dual Channel HighSpeed Optocoupler


56/7065

Servo Type DC Isolation Amplifier

Description The above schematic uses a dual-channel, high-speed optocoupler(HCPL-2530/1) to function as a

servo type dc isolation amplifier. This circuit operates on theprinciple that two optocouplerswill track each other if their gainchanges by the same amount overa specific operating region.

Performance of Circuit• 1%linearity for 10 V peak-to-

peak dynamic range

• Gain drift: -0.03%/°C

• Offset Drift: ±1 mV/°C• 25 kHz bandwidth (limited by

Op-Amps U1, U2)

Benefits• Simple coupling circuit for

analog signals

References1) HCPL-2530/1 Dual Channel

High Speed Optocoupler Technical Data


Alternative HP Parts1) HCPL-0530/1 Small-Outline

Dual Channel High SpeedOptocoupler

2) HCPL-5530/1, HCPL-6530/1Hermetic Dual Channel HighSpeed Optocoupler


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Analog Signal Coupling Using Pulse-WidthModulation

DescriptionPulse-width modulation is adigital conversion technique fortransmitting analog signalsbetween two isolated systems.

The above schematic shows anoscillator and a monostablemultivibrator combination whichgenerates digital pulses whosewidths are proportional to theanalog input. The digital pulsesare supplied to the input of HCPL-2601 High Speed DigitalOptocoupler. At the output of theoptocoupler, an integrator andlow-pass filter circuit convertsthe pulse-width modulated signal

back to the original analog signal.

Performance of Circuit• Maximum pulse-width

distortion (PWD) of HCPL-2601: 35 ns

• Signal bandwidth: limited bylinearity of analog circuit andPWD of HCPL-2601

Benefits• Digital techniques allow greater

control of accuracy of theanalog signal

References1) HCPL-2601 High Speed Digital


2) HP Application Note 951-2,

“Linear applications of Optocouplers”

Alternative HP Parts1) HCNW2601 Widebody High

Speed Digital Optocoupler

2) HCPL-0611 Small-Outline HighSpeed Digital Optocoupler

3) HCPL-5601 Hermetic HighSpeed Digital Optocoupler

4) HCPL-7101 50 MBd CMOSOptocoupler


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Analog Signal Coupling Using Voltage-to-Frequency Conversion

DescriptionVoltage-to-frequency conversionis one technique for transmittinganalog signals between twoisolated systems. The aboveschematic shows an analogsignal, VIN, converted into afrequency that is proportional tothe analog value of VIN. Thevariable frequency signal is thencoupled through by the HCPL-2601 High Speed DigitalOptocoupler. At the optocoupleroutput, the variable frequency isconverted back to an analogsignal with a frequency-to-voltageconverter. The operating frequency

for this circuit is up to 5 MHz,however, for higher frequencyoperation up to 25 MHz, theHCPL-7101 optocoupler may beused.

Performance of Circuit• Maximum pulse-width

distortion (PWD) of HCPL-2601: 35 ns

• Signal bandwidth: limited bybandwidth of analog circuit andPWD of HCPL-2601

Benefits• High speed digital techniques

allows large bandwidth analogsignals

• Nonlinearity of optocoupler is anot a design issue

References1) HCPL-2601 High Speed Digital


2) HP Application Note 951-2,

“Linear applications of Optocouplers”

Alternative HP Parts1) HCNW2601 Widebody High


2) HCPL-0611 Small-Outline HighSpeed Digital Optocouple


4) HCPL-7101 50 MBd CMOSOptocoupler


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Performance of Circuit• Maximum pulse-widthdistortion (PWD) of HCPL-2431: 25 ns

• Maximum propagation delayskew of HCPL-2431: 35 ns

Benefits• Digital techniques allow greater

resolution and large bandwidth

• Nonlinearity of optocoupler is anot design issue

DescriptionWhen better linearity and hightemperature stability arerequired, digital techniques canbe used to couple analog signals.

This technique is especiallyrecommended when an analogsignal will eventually be processedor recorded digitally. The aboveschematic shows two ways of sending A/D output signals: inserial or in parallel.

References1) HCPL-2430 High Speed DigitalOptocoupler Technical Data

2) HCPL-2530 High SpeedOptocoupler Technical Data

3) HP Application Note 951-2,“Linear applications of Optocouplers”

Alternative HP Parts1) HCPL-0631 Small-Outline High


2) HCPL-0531 Small-OutlineHigh Speed Optocoupler


4) HCPL-5531 Hermetic HighSpeed Optocoupler

Analog Signal Coupling UsingA/D Converters


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Analog Signal Multiplexing

Description The HSSR-8200 Solid State Relay(SSR) can be used for multiplex-ing one set of analog inputs fromseveral. In the above circuit, theselected analog input is presentedto a signal processor. Thedifferential inputs (H and L) areshielded by a guard (G) driven bythe processor. When open, thecontacts of the HSSR-8200 canwithstand 200 V, positive ornegative. Protection againstdamage due to exceeding 200 Vis provided by the metal-oxidevaristors DH,N, DL,N, and DG,N.

Performance of SolidState Relay• Output leakage current: 20 pA

(typical) at VO = 200 V

• Turn-on current: 1 mA• Output capacitance: 4.5 pF

(maximum)

• Output offset voltage: 0.2 µV(typical)

Benefits of Solid StateRelay• High output off-impedance and

low offset voltage allows highaccuracy measurement

• Small size lower power

dissipation

References1) HSSR-8200 Solid State Relay

Technical Data

2) Application Note: Small Signal

Solid State Relay

Alternative HP Parts1) HSSR-8400: 400 V Solid State

Relay

2) HSSR-7100 Hermetic SolidState Relay


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Description The HCPL-3700/60 Threshold-Sensing Optocoupler can be usedfor sensing the ac/dc power on/off condition. At the optocouplerinput, only a pair of seriesresistors RX/2 are required tolimit the current. The ac signalcan be filtered with a capacitor ateither the input or the output of the optocoupler. For moreinformation refer to HP Applica-tion Note AN 1004, “ThresholdSensing for Industrial ControlSystems.” The value of RXdetermines the threshold sensingvoltage.

Performance of Circuit• HCPL-3760 optocoupler

threshold input current: 1.3 mA(typical)

• Typical optocoupler propaga-tion delay: 10 µs

• Optocoupler common modetransient immunity: 600 V/µs(typical)

• Maximum input voltage: up to

1000 Vdc, or 800 Vac

Benefits• HCPL 3700/60’s built-in diode

bridge and hysteresis circuitreduces component count

• HCPL-3760’s low thresholdsensing current reduces powerdissipation

• Threshold voltage can beadjusted by external resistor RX

References1) HP Application Note AN 1004,

“Threshold Sensing forIndustrial Control Systems”

2) HCPL-3700/60 ThresholdSensing Optocoupler

Technical Data

Alternative HP PartsHCPL-57XX: Hermetic Threshold

Sensing Optocoupler

AC/DC Voltage Threshold Sensing

Industrial Applications


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Description The HSSR-8060 Solid State Relay(SSR) can be used for switchinglow-voltage incandescent lampsin industrial equipment. This SSRcan be controlled with TTL orCMOS 5V logic, and requires only5 mA for turn-on. For dc switch-ing, the HSSR-8060 output canpass up to 1.5 A steady-statecurrent, and 7.0 A transientcurrent.

Performance of SolidState Relay• Maximum output withstand

voltage: 60 V peak, eitherpolarity

• Typical output on-resistance:0.4Ω for ac connection; 0.1 Ωfor dc connection (refer toHSSR-8060 Solid-State Relay

Technical Data for an explana-tion of ac and dc connections.)

• Maximum output steady statecurrent: 1.5 A for dc connection;0.75 A for ac connection

Benefits• Greater reliability compared to

electro-mechanical relays

• Compact size

• With a low input turn-oncurrent of 5 mA and low outputon-resistance there is lesspower dissipation

References1) HP Application Note, Low On-

Resistance Solid State Relays

2) HSSR-8060 Solid-State Relay

Technical Data

Alternative HP Parts1) HSSR-7110/1 Hermetic Solid

State Relay

2) HSSR-8400, 400 V Solid-StateRelay

Low Power - AC/DC IndustrialSwitching


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Description The HCPL-2231 dual-channel,high-speed, optocoupler isolatesthe low-voltage logic circuit fromthe high-voltage Flat-PanelDisplay row/column drivers.Examples of Flat-Panel Displaytechnologies requiring such highvoltage technologies are Electro-Luminescence, Fluorescence, andPlasma technologies. Theoptocoupler serves the functionsof level shifting and safetyisolation.

Optical Isolation In Flat-PanelDisplays

Performance of Optocoupler• Maximum propagation delay

time: 300 ns

• Input turn-on current: 1.6 mA• Common-mode transient

rejection: 10,000 V/µs at1000V peak for the HCPL-2232

Benefits of Optocoupler• Compact size and easy

interface compared to pulsetransformers

• Low input current allowingCMOS interface

• Low component count (HCPL-2231/2 requires no pull-upresistor)

ReferencesHCPL-2231/2 Low Input CurrentOptocoupler Technical Data

Alternative HP Parts1) HCPL-0201/11 Small OutlineLow Input CurrentOptocoupler

2) HCPL-52XX series Hermetic,Low Input Current Optocoupler

3) HCNW-2201/11 WidebodyLow Input CurrentOptocoupler

4) HCPL-2430/1 20 MBd Logic-Gate Optocoupler

5) HCPL-7101 50 MBd CMOS

Logic Optocoupler


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Description The above circuit shows how theHSSR-8200 Solid State Relay canbe used for gain selection in anoperational amplifier circuit. TheHSSR-8200’s low offset andnegligible non-linearity when theoutput is closed ensures a lowerror over a four-decade range. Asimilar scheme with the HSSR-8200 can be used for gainselection in a non-invertingamplifier.

Gain Selection for Op-AmpCircuits

Performance of Solid-State Relay• Typical output offset voltage:

0.2 µV with IF = 1 mA

• Typical output on-resistance:125 Ω

• Typical output off-impedance:10,000 GΩ

Benefits of Solid-StateRelay• Smaller size and greater

reliability (compared to electro-mechanical relays)

• Reduced op-amp output error(SSR has low-offset voltage,

low output capacitance, andgood output linearity)

• Low power dissipation (only1mA turn-on current)

References1) HSSR-8200 Solid State Relay

Technical Data

2) HP Application Note 1036,

“Small Signal Solid StateRelay”

Alternative HP Parts1) HSSR-8400, 400 V Solid State

Relay

2) HSSR-8060, 60 V Solid StateRelay

3) HSSR-7110/1, Hermetic SolidState Relay


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DescriptionIn battery-powered alarmsystems, the alarm circuit needsto be disconnected from thebattery when not in use. TheHSSR-8060 Solid State Relayreconnects the alarm circuit tothe battery only when the sensorcircuit is energized.

Performance of SolidState Relay• Typical output on-resistance

=0.4 Ω for ac-connection;0.1Ω for dc-connection (referto HSSR-8060 Solid-State Relay

Technical Data for anexplanation of ac and dcconnections.)

• Maximum output steady-statecurrent: 1.5 A for dc-connection;0.75 A for ac-connection

• Maximum output withstandvoltage: 60 V peak (eitherpolarity for ac-connection)

Benefits of Solid State

Relay• Greater reliability compared to


• Compact size

• Less power dissipation (lowinput turn-on current, and lowoutput on-resistance)

References1) HP Application Note 1046,

“Low On-resistance Solid StateRelays”

2) HSSR-8060 Solid State Relay Technical Data

Alternative HP Parts1) HSSR-8400, 400 V Solid State

Relay


Low Power Alarm Control Circuit


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Description The HSSR-8060 Solid State Relay(SSR) can be used for driving thecoil of a large electro-mechanicalrelay. This SSR can be controlledwith TTL or CMOS 5 V logic, andrequires only 5 mA for turn-on.Diode D1 across the coil of theelectro-magnetic relay protectsthe SSR output by limiting theback EMF of the coil during turn-off. The HSSR-8060 can switchup to 7.0 Amp transient currentwhen the output is in the dc-connection.

Performance of SolidState Relay• Maximum output withstand

voltage: 60 V peak (eitherpolarity for ac-connection)

• Typical on-resistance = 0.1 Ωfor dc-connection

• Maximum steady-state current:1.5 A for dc-connection; 0.75 Afor ac-connection (refer toHSSR-8060 Solid-State Relay

Technical Data for anexplanation of ac and dcconnections.)

Benefits of Solid StateRelay• Greater reliability compared to


• Compact size

• Less power dissipation (lowinput turn-on current, and lowoutput on-resistance)

References1) HP Application Note 1047 and

1046, “Low on-resistance SolidState Relays”

2) HSSR-8060 Solid State Relay Technical Data

Alternative HP Parts1) HSSR-7110/1 Hermetic Solid

State Relay


Relay Coil Driver


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DescriptionSwitching power supplies oftenneed to couple digital and analogsignals between the primary andsecondary circuits. The aboveschematic shows an analog errorsignal representing the differencebetween the output voltage andthe reference voltage being fedback to the primary side using aHCNR200/1 Analog Optocoupler.

The analog error signal helps thepulse-width modulation (PWM)controller determine the exactpulse-width to make the filteredoutput voltage match the systemreference voltage. In a similarmanner, the HCNW136 DigitalOptocoupler can be used tomonitor the primary side power-off and under-voltage condition.

Performance of Optocoupler• HCNR200/1 has 0.01% non-

linearity and up to 1 MHzbandwidth

• HCNW135 has 0.2 µs typicalpropagation delay time

• Both HCNR200/1 andHCNW136 optocouplers meetworldwide regulatory insulationguidelines

Benefits• Accurate monitoring and con-

trol of secondary output voltage

• Power off condition detectableat an early stage enabling themicroprocessor to save criticalinformation

References1) HCNR200/1 Analog


2) HCNW136 High SpeedOptocoupler Technical Data

Alternative HP Parts1) HCPL-7800/7820 Isolation

Amplifier

2) HCPL-4503, HCNW4503 High

CMR Digital Optocoupler3) HCNW2601/11 Widebody,

High Speed DigitalOptocoupler

Optical Isolation In A Switching Power Supply -Circuit No. 1

Power Supply Applications


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Optical Isola

Documents

Designer's Guide to Isolation Circuits