Upload
others
View
8
Download
0
Embed Size (px)
Citation preview
AN50
AN50U 1
AN50 OptimizingPowerDeliveryinPWMMotorDriverICs
Thermal Behavior of Single-Phase, Three-Phase Single-ChipPWM Amplifiers SA57-IHZ, SA306-IHZ
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Device Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Optimizing Thermal Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 OptimizingMotorCommutationMethods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 BalancingtheElectricalLoad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 DefiningaMovementProfile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Cooling Options and Results with the 64-pin QFP Package . . . . . . . . . . . . . . . . . . . . . . . . . . 7 SMTMountingwithoutHeatsinkinLow-PowerApplications . . . . . . . . . . . . . . . . . . . . . . . . . 7 SMTMountingwithThermalPadandHeatsinkforMid-RangePowerApplications . . . . . . . 9 Flipped-OverSMTMountingwithHeatsinkforHigh-PowerApplications . . . . . . . . . . . . . . . 11 ComparisonsofLow-Power,Mid-RangePowerandHigh-PowerTestBoards . . . . . . . . . . 13 HighPowerHeatSinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 PowerDissipationDerating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Appendix Derivation of Maximum Power and Thermal Dynamic Values . . . . . . . . . . . . . . . 22 SMTMountingWithoutHeatsinkinLow-PowerApplications . . . . . . . . . . . . . . . . . . . . . . . . 22 SMTMountingwithaThermalPadandHeatsinkforMid-RangePowerApplications . . . . . 23 Flipped-OverSMTMountingwithHeatsinkforHigh-PowerApplications . . . . . . . . . . . . . . . 24
AN50Optimizing Power Delivery in PWM Motor Driver ICs
Copyright © Apex Microtechnology, Inc. 2012(All Rights Reserved)www.apexanalog.com OCT 2012
AN50U REVB
AN50
2 AN50U
IntroductionTheApexSA306-IHZ isanadvanced3-phasesinglechipamplifier,designedforuseasan independentpowerstagetodrive3-phasebrushlessDCmotors .Itincorporatesa3-phasePWMamplifierthatacceptssixindependentcontrolsignals .Thisenablesadesignertochoosefromawidevarietyofcontrolsignalsasappropriateforthecom-mutationmethodchosen .ThisApplicationNotediscussesdifferencesinthethermalbehaviorofthedevicerelatingtomountingtechniques,methodsofmodulationofthepowerstageandexaminessometechniquestoimprovesystemperformanceandoverallefficiency .Inordertochoosetheappropriatethermaldesignforaparticularapplicationandforthebasicdimensioningoftheheatsink,thecalculationofthefirst-orderthermalapproximationisagoodstartingpoint .Therearesomeapplica-tionspecificaspectstobetakenintoaccountbeforestartingthebasicsystemdesign .ThisApplicationNotecoverssomeofthesebasicdesignsteps,dataandideastocarryforwardsothedesigncanachievethebestresults .
Device OverviewBoth theSA306-IHZandSA57-IHZdevices incorporateallof thesub-systemsnecessary todriveabrushedorbrushlessDCmotorunderthecontrolofanMCUorDSP .Atmaximumoutputthesedevicesarecapableofsafelyoperatingmotorsapproaching0 .5hp .Likemanytraditionalmotordriveproducts,SAdevicesintegratecontrol,pow-ersupply,gatedriveandpowerstageintoasingleIC .Unlikecompetingdevices,thisseriesisspecificallydesignedforMCUorDSPcontrolandintegratefeaturesthatenableimplementationofmoderncommutationtechniques,re-sultinginhigherefficiencydrivestages .BothSA306-IHZandSA57-IHZdevicesconsistofmajorblocks,asshowninFigure1 .Theprimarydifferencebetweenthetwodevicesisthenumberofphasessupported;theSA306-IHZsupportsthreephaseswhiletheSA57-IHZsupportstwo .Akey featureof thisseries is theability todirectlycontrol theoutputFETs .Thisenablesmoderncommutationschemessuchasfield-oriented,vector-oriented,andsinusoidaltobeimplementedwithinthecontrollerwithnoin-
SA306 Switching Amplifier
BRUSHLESSMOTOR
Vs (phase A)
PGND (A&B)
CurrentmonitorSignals
Sensor – Hall SensorsorSensorless – Input from Stator leads
AB
C
OUT AOUT BOUT C
PGND (C)
GND
Vs (phase B&C)
Vs +
Sensingcircuits
GND
SGND
GateControl
ControlLogic
FaultLogic
TEM PILIM/D IS1
SC
Ia
IcIb
VDD
PWMSignals
DIS2
SG ND
AtAb
BtBb
CtCb
M icrocontrolleror DSC
Figure 1. System Block Diagram using the 3-Phase SA306-IHZ Device
AN50
AN50U 3
terveningcircuitry .ThisarchitecturesimplifiescircuitdesignandreducesEMC/EMI .ThesedevicestaketheinputsforeachgateandprovidesbufferinganddrivetothecompanionFET .Anothersignificantfeatureisbuilt-incurrentsense .Currentsenseisavailableforeachofthephasesfromasepa-rateoutputpin .Theoutputcurrentof thesensepins is~1/5000thof thephasecurrent .Thecurrentsensepinsprovidedirect,real-timefeedbacktothecontroller .Currentsenseisperformedatthehigh-sideonly .Sensingoflow-sidecurrentsunderbrakingorflybackconditionsisnotsupported .Over-temperature,short-circuitandcurrentlimitarealsoimplemented .Thesefaultsignalsprovideimportantfeed-backtothesystemcontrollerwhichcansafelydisabletheoutputdriversintheeventofafaultcondition .ThesetopicsarediscussedingreaterdetailinReference3 .Both theSA306-IHZandSA57-IHZ implementacycle-by-cyclecurrent limitscheme .Thisallowsvariableuser-definedcurrentlimitthresholdswithoutdamagetothedevice .However,eveninthismode,theusermustconsiderandplanforexcessivecurrentexcursionswhichcouldresultinexcessivepowerdissipation .ThearchitectureoftheSA306-IHZandSA57-IHZdevicesenablesthedesignertoconfiguredynamically-changingcurrentlimitinginthedeviceinresponsetochangingsystemoperatingconditions .TheSA306-IHZorSA57-IHZdatasheetsspecifyapeakcurrentof17amperes .However,ifdesiredthedesignercanchoosetolowerthislimitortodisablethefeaturealtogether .Inapplicationswherethecurrentinthemotorisnotdirectlycontrolled,boththeaveragecurrentratingofthemotorandtheinrushcurrentmustbeconsidered .Forexample,a1Acontinuousmotormightrequireadriveamplifierthatcandeliverwellover10APEAKinordertoprovidetherequiredstart-uptorque .Thecycle-by-cyclecurrentlimitfeatureenablestheSA57-IHZ/SA306-IHZtosafelyandeasilydriveawiderangeofbrushandbrushlessmotorsthroughastartupinrushcondition .Withlimitedcurrent,thestartingtorqueandaccelerationarealsolimited .TheplotsinFigure2illustratestartingcurrentandbackEMFwithandwithoutcurrentlimitenabled .
MoreinformationontheseandotherfeaturesoftheSA306-IHZandSA57-IHZcanbefoundintheproductdatasheets,aswellasanyassociatedApplicationNoteslistedintheReferencesectionfoundattheendofthisdocu-ment .
Optimizing Thermal PerformanceAllpowerdevices,fromFETsandIGBTstolargemicroprocessors,dissipatepowerintheformofheat .Fordeviceswhoseprimarypurposeispowerconversionorpowertransmissionappropriatemanagementofheatisthekeytodetermininghowmuchpowercanbesafelyprocessedbythedevice .Thisfactappliestospecificationlimitsaswell .Adevicemayberatedfor5Acontinuousbutthesystemdesignermustalwaystakecarethatthepowerlostintheformofheatdoesnotresultindamagetothedevice .Itmustbenotedthattotaloutputpowerandtotalpowerdissipationaredependentonboththeoutputcurrentandoperatingvoltage .ForallmountingtechniquesdiscussedinthisApplicationNotetheeffectofvoltageandcurrentlevelswillproducevariationsinpowerdissipation .Forexample,graphsoflowpoweroperationshowheatdissipa-tionforagivenoutputpower .BecausepowerdissipationfollowstheformulaP=I2R,increasingoperatingvoltagetothehighestpracticallimitwillresultingreateroutputpoweratagivencurrent(internalpowerdissipation) .Con-verselypowerdissipationcanbereduced foragivenoutputpowerby increasingvoltageandreducingcurrent .
Time, Milliseconds
NON-LIMITED BACK EMF
NON-LIMITED MOTOR CURRENT
Cur
rent
, Am
pere
s
Time, Milliseconds
Cur
rent
, Am
pere
s
LIMITED BACK EMF
LIMITED MOTOR CURRENT
(a) (b)
Figure 2. Motor Current Behavior at Startup — (a) Without cycle-by-cycle current limit. (b) With cycle-by-cycle current limit
AN50
4 AN50U
Graphsaregenerallynotprovidedformultiplecombinationsofcurrentandvoltage .Rathertheemphasisisonthecalculationofpowerdissipationandthermalresistance,thusenablingthede-signertocalculatedietemperatureforthesystem'scombinationofvoltage,current,andheatsinking .ShowninFigure3isaninfraredimageofaSA57-IHZdrivingabrushedDCmotorwithacontinuouscurrentof3Aatasupplyvoltageof24V .Thenumbersmarkthelocaltemperaturesofthedesign .Thehighandlow-sideFETsoftheactivehalf-bridgecanclearlybeseenaswhitedots,representingatemperatureofap-proximately110°C .Thispictureshowsthetemperaturegradientsacrossthesilicon .Theheatgeneratedatthetwohot-spotsspreadsoverthesiliconarea .The result isa core temperatureofapproximately90°C .TheredarearepresentstheheatslugoftheIC .Thistemperatureisnearlyequaltothecoretemperatureofthesilicon .Theheatistransferredtotheheatsinkonthebackside(yellow)andinthiscasetothetopandbottomlayer(green)ofthePCB,thendis-sipatedintotheambientair .(Notethattheapparenttemperaturedifferenceofthescrewsistheresultofemissivitydifferencesbe-tweenthescrewsandtherestofthetestsystem .Insteady-stateoperationthescrewsareapproximatelythesametemperatureastheheatsink) .
Optimized Motor Commutation MethodsTheON-resistanceofthepowerFETsistheprimarycontributortoheatgenerationwithinamotordrive .Incalculat-ingthepowerlosttotheONresistanceweusethestandardpowerformulaP=I2R,whereI=thecurrentflowingthroughthemotorandR=theON-resistanceoftheIC .AstheSA57-IHZandSA306-IHZofferdirectaccesstoeachsingleFET,itispossibletousealternativecommutationtechniquestoincreasethesystemperformanceandtoreducethermalloads .Thebestexampleforasimplesystemoptimizationissinusoidalcommutationofa3-phasebrushlessDCmotor .Thismethodoffersincreasedefficiencyandreducedpowerdissipation .Alternatetypesofcommutationaremorefeasiblenowthatvirtuallyeverymotorcontrolsystemhassometypeofmicro-controllerorDSP/DSCavailable .
4.608
4.096
3.584
3.072
2.560
2.048
1.536
1.024
.512
0
-.512
-1.024
-1.536
-2.048
-2.560
-3.072
-3.584
-4.096
-4.608Single FET Control
Phase BDual FET Control
Phase B/CSingle FET Control
Phase CDual FET Control
Phase C/ASingle FET Control
Phase ADual FET Control
Phase A/B
Dual FET ControlPhase C/A
Single FET ControlPhase A
Dual FET ControlPhase A/B
Single FET ControlPhase B
Dual FET ControlPhase B/C
Single FET ControlPhase C
PWM
Dut
y C
ycle
as
12-B
it Va
lue
(BIT
)
60° 120 ° 180° 240° 300° 360°
Low-Side MOSFETS
High-Side MOSFETS
Rotor Angle
Figure 3. Infrared picture of a SA57 running at 3 amperes at 24 volts.
Figure 4. Power and voltage behavior in the case of 3-phase sinusoidal commutation.
AN50
AN50U 5
Sinusoidalcommutationofa3-phaseBLDCmotorspreads thegeneratedheatoverawiderareaof thesiliconthanwithblockcommutation .Thisreduceslocalizedheatinginthedie .Duringsinusoidalcommutationthecurrentthroughthemotorisdeliveredbytwohigh-sideFETsandasinglelow-sideFETor, inthenextstep,byusingasinglehigh-sideFETandtwolow-sideFETs .ThismeansthattherearealwaystwoactiveFETsinparallelwhichdecreasestheONresistanceofthetwoparallelconductingFETs .Theresultingresistanceisnotlinearbecausetheon-timeofeachPWMsignalofthetwoFETsconnectedinparallelfollowsasinωt/cosωtrelation .(SeeyellowareasinFigure4)TheeffectiveONresistanceacrossanelectriccommutationcyclecanbecalculatedbydividingtheON-resistancevalueoftheparallelhighorlowsideFETsby√2 .Usingthiscommutationtechniquecan,inadditiontoseveralotheradvantages,reducethethermalloadbyapproximately10%to15% .Theundissipatedpowercanbeusedtodrivethemotorortoreducethetotalpowerconsumption .Ineithercasetheoverallefficiencyofthesystemisincreased .
Balancing the Electrical LoadAswehavejustdiscussed,themainheatgeneratingcontributor isthecurrentflowingthroughthepowerFETs .BecausetheSA57-IHZandtheSA306-IHZarehigh-voltagedevicessuitableforsupplyvoltagesupto60V,anin-creaseinthesupplyvoltagecanleadtoadecreaseofthecontinuouscurrentforagivenpowerlevelandthereforetoadecreaseofthethermalload .Fromthispointofview,thebasicideaistoincreasethesupplyvoltagewhilekeepingthecontinuouscurrentcon-stanttoreducethethermalload .Inapulse-drivensystemwithaninductiveload,therelationbetweenvoltageandcurrentisnotlinearsowehavetotakeacloserlookatswitchinglossesandthecurrentcharacteristicsundervari-ousoperationconditions .An application is balanced when the for-wardandbackwardmagnetizationofthein-ductorisfullyrealizedwithinasinglePWMcycle .Thisshouldbethenormaloperatingconditioninapplicationswithconstantrota-tionspeedandlowdynamics,suchasfans,pumpsorunidirectionaldrives .Intheseap-plications,onceaccelerated,themotorrunsat a constant speed with a constant me-chanicalload .Shown in Figure 5 are the characteristicsof the voltage and current during a PWMpulseinabalancedoperatingsituation .Therisingand fallingedgesof thevoltagearenearlylinearwithintheperiodgivenbythetimevaluefortheraisingandfallingedges– typically 200 nanoseconds . The currentcharacteristicdependsonthetechnicalpa-rameters of themotor winding . Thewind-ings produce a reverse voltage when therisingedgeoccurs .Thecurrentreachesitsmaximumwhenthesupplyvoltageandthereversevoltagearemoreor lessequal .Theresultingphaseshift isrepresentedbytVI .Whenthesupplyvoltagev3isbeingincreased,thephaseshifttVIbecomeswiderasshownbyarrowv1andtherisingedgeofthecurrentv2appearslater .Theterminationofthedutycycleshutsdownthecurrentimmediatelyandalwaysatthesamepointintime .Sowhenthesupplyvoltageincreases,bothcurveschangeinthedirectionsindicatedbythearrowslabeledv1,andv2 .ShowninFigures6and7arevoltageandcurrent(overshootnotvisible)plotsresultingfromaPWMpulseappliedtophaseA .Both10Vand30Vsupplyvoltagesareshown .WhenwelookatthefallingedgeofthePWMpulse,weseethatthecurrentdropswiththesameslewrateatasup-plyvoltageofboth10Vand30V,butforalongertimeintervalbecauseofthehigherpeakcurrent .Thismeansthattheswitchinglossesincreaseonthefallingedge .AttherisingedgeofthePWMpulsethecurrentisless,sothattheswitchinglossesonthissidehavedecreased .
Voltage
Currentt(rise) t(fall)
t(VI)
Time
v1
v2v3
Cycle Termination
Figure 5: Characteristic of voltage and current during a PWM pulse in a balanced system
AN50
6 AN50U
Whenwecomparethetotalaveragecurrentovertime,wefindsimilarvaluesatasupplyvoltageof10Vand30V .Althoughthepeakcurrentat30Visapproximately30%higher,thepulsewidthis20%shorterandtheslopeofthepulsetopissteeperthanat10V .Inanoverallcomparisontheaveragecurrentofbothpulsesisnearlyconstantwithslightlyincreasedswitchinglosses .Becausetheaveragecurrentremainssimilar,theaveragetemperatureduetoI2RlosseswithintheFETsisalsosimilar .However,becausevoltagedeliveredtothemotordoesincrease,thereisgreaterpoweravailabletothemo-torwindings .Thisfactresultsinincreasedefficiencybydrivingmotorsathighervoltages .
Defining a Movement Profile Insomeapplications,suchasservodrivesforpositioningorrobotics,wefindawidevarietyofspecificoperationmodes, includingperiodicaccelerationor stalledmotoroperationwithhigh torqueand low rotational speed . Intheseoperatingmodesthesystemisnot“balanced”sincethemotorwindingsarenotallowedtoachievecompleteforwardandbackwardmagnetizationwithinasinglePWMcycle .Intheseconditionsthemotorwindingscanbecomeoverenergized,orsaturatedwithpower .Asthisbeginstooccur,increasedmotorcurrentnolongerproducesproportionalincreasesintorqueandincreasedheatingcanoccurintheFETsofthedevice .Insomecasesthemotorwindingsareoverenergizedtoobtainthetorquerequiredtobrakethemechanicalload,resultinginamajorchangeofthecurrentwaveformcharacteristic .
20
10
0
-10
VD
C
0 10 20 30 40 50 60 70 80 90 100 Microseconds
Am
pere
s
30
20
10
0
-10
0 10 20 30 40 50 60 70 80 90 100Microseconds
VD
CA
mpe
res
40
Figure 6. Voltage (green) and current (blue) during a PWM pulse on phase A at a supply voltage of 10 V DC, a 25 kHz switching frequency and a 50% duty cycle.
Figure 7. Voltage (green) and current (blue) during a PWM pulse on phase A at a sup-ply voltage of 30 V DC, a 25 kHz switching frequency and a 50% duty cycle.
AN50
AN50U 7
In thesemodes of operation, tVI becomes smaller and a highcurrentpeakappearsattheraisingedgeofthePWMpulseasshowninFigure8 .Themorethesupplyvoltagev3increasesthehigherthecurrentpeakv2willbe .Thiscurrentpeakcanreachmultiplesofthecontinuouscurrent .TheplotsinFigure9depicttherelationshipbetweendutycycle,continuouscurrentandtemperatureatasupplyvoltageof20VDC .ByseparatingtheperformancegraphinFigure9intotwoparts,thebalancedoperation(A)andtheoverenergizedoperation(B)canbebetteranalyzed .Duringbalancedoperation,thecurrentandvoltagewaveformsfollowtherelationshipsshowninFigure5 .Thephaseshift tVI increasesso that thecontinuouscurrentandtemperatureincreaseonlyslightly .Whenthemotorwindingstartsbeingoverenergized(B),tVIdecreasesrapidlyasshownin Figure 8 .The current peak at the rising edge of thePWMcycleincreasesthetotalaveragecurrentandthethermalload .Overenergizedconditionsnormallyhappeninthe60-70%dutycyclerange .ThisrangecorrespondswiththekneeofthecurvesinFigure9 .Theexactpointisdependentonboththequalityofthemotorandtheoperatingcondition .Theoperatingconditionwith theexpectedmaximal thermal loadand itsmaximal timeintervalisthebasisfortheselectionofthebestmountingtech-niqueandheatsinkingmethod .The64-pinPowerQFPpackageused for theSA306-IHZandSA57-IHZ lends itself to different kinds ofmounting and heatsinking options which can be used under different operatingconditionstorealizethebestresultsaccordingtoperformanceandtotalsystemcost .Inthefollowingsectionssuggestionsareprovidedonhowtoselectthebestsolutionforyourapplication .
Cooling Options and Results with the 64-pin QFP PackageThe size and orientation of the heatsinkmust be selected tomanagetheaveragepowerdissipationofthedriverICs .Applica-tionsvarywidelyandvariousthermaltechniquesareavailabletomatchtherequiredperformance .Thissectiondiscussesseveraltechniquesthatareappropriatefordifferentpowerlevels .Thefollowingexamplesweredevelopedtoevaluatedifferentmountingandcoolingoptionsandtodefinetheirbasiccapabilities .DerivationofmaximumpowerandthermalsystemdynamicsisshowninAppendixA .Twodifferentsetsof testswereconductedon theSA306-IHZ .For thefirstsetof tests thepowerdevicesweremountedonaPCBwithaDigitalSignalController(DSC) .ThisDSCoffersanenhancedmotioncontrolinterfaceandallowsadesignertocommutatethemotorindifferentways .Forthesecondsetoftestsapowertestbenchwasusedtoshowtheeffectofsteadystatecurrentsonpowerdissipationandthermalperformance .
SMT Mounting without Heatsink in Low-Power Applications ThemostcosteffectivewayofmountingeitheroftheSA306-IHZorSA57-IHZdevicesistosolderthemdirectlyonaPCBwithoutanyfurtherheatsinkingcomponents .Theheatslugofthe64-pinQFPpackageoffersoptimizedheattransfertothePCB(asshowninFigure10) .TheICpackage,includingtheheatslug,canbesolderedtothetoplayerofthePCB .Beneaththeheatslug,severalviascanbeusedtooptimizeheattransfertothebacksideoftheboard .Thecopperareausedforthepowergroundisalsousedforbetterthermalcouplingtotheambientair .Aspartofthetests,semiconductortemperaturesensorwasplacedinthemiddleoftheheatslugareatomeasurethebackside(maximum)heatslugtemperature .Atanoutputpowerof20W,atemperaturegradientof99 .6°Kwasobtained .Thisindicatesthatthejunctiontemperaturewillbeapproximately130°Catanambienttemperatureof30°C .TheplotsinFigure11denoteavalueof136°Catanambienttemperatureof27°Cwithatotalthermalresis-tanceforthesystemofapproximately5 .343K/W .
Voltage
v1
v3
Currentt(rise) t(fall)
t(VI)
Cycle Termination
v2
v1
Time
) )
Duty Cycle @ 20V DC [%]
Tem
pera
ture
[°C
]
Con
tinuo
usC
urre
nt [A
]Temperature [°C]
Continuous Current [A]
AB
Figure 8. Voltage (green) and current (blue) during a PWM pulse over energizing a mo-tor winding
Figure 9. Temperature and continuous cur-rent vs. PWM duty cycle during a stalled motor operation
AN50
8 AN50U
Using the thermal resistance value, the maxi-mumoutputpowercanbecalculatedforanappli-cationcoveringtheindustrialtemperaturerangeupto+85°Catapproximately9W .Thisresultisvalid for static operation under the specific setofvoltageandcurrentconditions .Inapplicationswith frequentaccelerationsanddecelerations itisimportanttoknowthethermalresponsetime .Thisvalueprovidesanindicationforthetimere-quiredtotransferaspecificamountofheatfromthedietothebacksideoftheboard .Derivationsforcalculatingthermalresistanceandmaximumpowerdissipation canbe found inAppendixA .ShowninFigure12isthetemperaturecharacter-isticofthegroundplanefromtheambienttothemaximumtemperaturewhenthemotorisdrivencontinuouslyatanoutputpowerof9W .
ConclusionAlthoughthemaximumoutputpowerratingof8Wto9Wseemslow,thesedevicesarestillcapableofdeliveringPEAKcurrentsupto15Aforseveralseconds .Inaddition,increasedvoltageorreducedambienttemperaturemayresultinincreasedpowercapability .ThismakestheSA57-IHZandSA306-IHZunusuallywellsuitedforapplicationsusinggearswithhightransmissionrateswherelargemechanicalloadshavetobeacceleratedthroughstart-upphaseandendathighspeedswithlowerpowerrequirements .Thismountingtechniqueisappropriateforsmaller,low-powerorhigh-speeddrivesincostsensitiveapplicationssuchasfans,pumps,scanners,surveillancecameras, labelingmachinesorpaperfeeders–allwheresizeandproductioncostsarecrucial .
SMT Mounting with Thermal Pad and Heatsink for Mid-Range Power ApplicationsForapplicationswherehigheroutputpowerisrequiredforalongerperiodoftime,buteaseofproductionisstillamaindesignissue,anadditionaltestboardwasdesignedwheretheSA306-IHZisstillmountedintheconventionalmanner .However,beneaththeICisa100mm²cutout .AthermalpadisusedtotransfertheheatfromtheheatslugdirectlytotheHS33heatsink .Thethermalpadismadefromapolymerthatcontainsmaterialschosenforlowthermalresistance,suchassilver .Thesepadsremainsoftforyearsandthereforecanaccommodateanyshiftingthatmayoccurtoequalizebetweenmaterials
Thermal Response Time at MAX. Output Power
100
120
140
Hea
t Slu
g Te
mpe
ratu
re [°
C]
- Common SMT Mounting Technique -
0
20
40
60
80
Time [sec]
t30
T30
T90t90
0 16014012010080604020
GroundPlane
HeatSlug
TemperatureSensor
HEAT SLUG TEMPERATURE VS.ELECTRICAL OUTPUT POWER
- COMMON SMT MOUNTING TECHNIQUE -
0
20
40
60
80
100
120
140
160
0 5 10 15 20Total Electrical Power [W]
Hea
t Slu
g Te
mpe
ratu
re [°
C]
Block Commutation
Sinusoidal Commutation
Figure 10. Bottom layer of the PICtail™ plus test board for low power applications
Figure 11. Temperature characteristic of the SA306-IHZ mounted on test board for low-power applications
Figure 12. Thermal response time at MAX output power of 9 W
AN50
AN50U 9
withdifferentcoefficientsofexpansionthatislikelytooccurduetotemperaturechanges .Onthemid-powertestboarda2mmthermalpadisusedtofillthegapbetweentheheatslugandtheheatsink(seeFigure13) .ThethermalpadchosenisaBerquistTMGapPad5000S35 .Thecutoutareais10mmx10mm .
Thisboarddesignprovidesthreeadvantages:• TheSA306-IHZisstillmountedlikeaconventionalSMTpart,includingtheside-wingsoftheheatslug .• Thermalcouplingisalwaysconstant,evenifthethicknessofthePCBsvariesfrom1 .5mmto1 .7mm .• Accurateplacementoftheheatsinkisnotrequired .
ShowninFigure14isthebackofthemid-powertestboard .The100mm²heatslugarea(red)hasbeencutouttoaccom-modatethethermalpad .ThetemperaturesensorhasbeenmovedtoanaturalcutoutoftheHS33heatsink .Theheightofthesensorpackageisexactlytheheightofthecutout .Thethermalcouplingcomesaboutduetotheintimatecontactofthepackagetopwiththeheatsink .Theheatsinkismountedwithtwoscrews .Notethatthelightgreenareaoftheheatsinkhasdirectcontactwiththedark-greengroundplanearea .Withthismountingtechniquethetotalthermalresistanceisreducedwhilethecontactareaisincreasedtoambientair .AlthoughtheHS33heatsinkisusedonthistestboard,itisnotessential .Athermalpadcouldalsobeusedtocoupletheheatslugtotheenclosuretoimprovethethermalpath .The100mm²x1 .5mmthickthermalpadwithitsthermalconductivityof86W/mKhasathermalresistanceof0 .174K/W .Whenthisvalueiscomparedtothe
SiliconHeat Slug
Package Lid
Power FETs
PCB
Dissipated Heat QEM
Thermal Pad
HS33 Heatsink
SiliconHeat Slug
Thermal Pad
Figure 13. Simplified cross sectional view of the thermal system of the mid-power test board
GroundPlane
HeatSlugTemperatureSensor
Figure 14. Bottom layer of the test board for mid-range power applications
Heat Slug Temperature vs Electrical Output Power
-
0.
20
40
60
80
100
120
140
160
Hea
t Slu
g Te
mpe
ratu
re [°
C]
Common SMT with Heatsink and Thermal Pad -
0
.0
.0
.0
.0
.0
.0
.0
.0
0 10 20 30 40 50 60Total Electrical Power [W]
Block Commutation
Sinusoidal Commutation
0.
Thermal Response Time at MAX Output Power- Common SMT Mounting Technique -
00 20 40 60 80 100 120 140 160
Time [sec]
20
40
60
80
100
120
140
Hea
t Slu
g Te
mpe
ratu
re[°
C] t90
T90
T30
t30
Figure 15. Temperature characteristic of the SA306-IHZ mounted on the test board for mid-range power applications using a thermal pad and the HS33 heatsink
Figure 16. Thermal response time at output power of 20 W
AN50
10 AN50U
previousmodelwithvias,thissolutionprovideslessthana10thofthethermalresistance .Usingthethermalpad,approximately51Wofcontinuousoutputpowerisachievedwithdietemperaturesofapproximately+155°Catanambienttemperatureof+26°Cusingblockcommutation .Themaximumpoweroutput,up to+85°Cfor thisconfiguration isap-proximately20Watthechosenvoltageandcurrent .Withthisso-lution it ispossible todouble theoutputpowerat similar systemtemperatures .Whatismostimportantistheimprovedperformanceovertheshortheatpathtotheheatsinkdueinparttothelowther-malresistancethroughthethermalpad .
ConclusionThethermalpadofferseasysystemassemblyandgoodthermalperformanceatmoderatepowerratings .Theshortthermalpathaf-fordsbenefitsinacceleratingheavymechanicalloadsforalongertime .Thisisanappropriatesolutionforawidevarietyofindustrialapplicationsusinggearsandwithproductionrunsinmid-rangevol-umes .
Flipped-Over SMT Mounting with Heatsink for High-Power ApplicationsThe third test boarduses the sameheat sinkingmethodas theApex Microtechnology Evaluation Boards DB63R and DB64R .ThistechniqueisalsodescribedintheHigh-Power Heatsinkingsection .This time the SA306-IHZ is flipped over and mounted . TheheatsinkisthenmounteddirectlyontotheheatslugoftheIC .ThisshortensthethermalpathfromtheICtotheambientairandreducesthetotalthermalresistanceofthesystemtoamin-imumof1 .674K/W .ShowninFigure17istheassemblyoftheICandheatsinkonthetestboardforhigh-powerapplications .Thepositionofthetemperaturesensor,themountingmethodoftheheatsinkandthethermalcouplingtothegroundplanearestillthesame .Theonlydifference is that theSA306-IHZ isflippedoverandsol-deredinaprecisecutoutfromthebacksideoftheboard .Apic-tureoftheactualmountingtechniquecanbeseeninFigure20 .As a result of thismounting technique, the characteristics ofthetemperatures inFigure18becomequite linearacrossthewholepowerrange .Theoutputpoweratadietemperatureof135°Cisapproximately52Wat+25°Candapproximately29Wat+85°C .Thissolutionprovidesonlyaslightlyhighermaxi-mumoutputpower than the thermal pad .However, the shortthermalpathhas itsadvantages indynamicapplications .Thefastresponsetimebetweenthedieandtheheatslugprovidesbenefitsinapplicationswheremultipleaccelerationsoccurovershorttimespans(seeFigure19) .
ConclusionTheprincipaladvantageoftheflipped-overmountingisthat itprovidesashortheatpathforsupportinghighdynamicapplica-tions .Thefreeaccesstotheheatslugoffersawidevarietyofheatsinkingmethodsandmoreeffectivecoolingoptions .
GroundPlane
HeatSlugTemperatureSensor
Heat Slug Temperature vs Electrical Output Power
0
20
40
60
80
100
120
140
160
180
Hea
t Slu
g Te
mpe
ratu
re [°
C]
- Flipped-Over SMT w. Heatsink HS33 -
0 10 20 30 40 50 60 70Total Electrical Power [W]
Block Commutation
Sinusoidal Commutation
Figure 17. Bottom layer of the test board for high-power applications
Figure 18. Temperature characteristic of the SA306-IHZ mounted flipped over on the test board for high power applications using the HS33 heatsink
Figure 19. Thermal response time at a output power of 25 W
Thermal Response Time at MAX Output Power- Common SMT Mounting Technique -
00 20 40 60 80 100 120 140 160
Time [sec]
20
40
60
80
100
120
140
Hea
t Slu
g Te
mpe
ratu
re[°
C] t90
T90
T30
t30
AN50
AN50U 11
Comparisons of the Low-Power, Mid-Range Power and High-Power Test BoardThefollowingtablecomparesthebenchmarkvaluesforeachmountingtechniqueinaside-by-sidecomparison .Pleasenote that thecolumns for themaximumoutputpowerare rated forambient temperaturesof+25°Cand+85°C .ThereisamoredetailedchartforthepowerdissipationderatingacrossambienttemperaturesinthePower Dissipation Deratingsection .
Table 1. Temperature characteristics of the SA306-IHZ mounted flipped over on the PICtail™ Plus test board for high-power applications using the HS33 heatsink
MountingTechnique
Calculated MAX Output Power@ +85°C (W)
MAX Output Power at
Test Voltage@ +25°C (W)
MAX Continuous Current at Test
Voltage@ +25°C (A)
Total Thermal Resistance RTH (K/W)
Average Ther-mal Response
Time k90(K/sec)
CommonSMT 9 .0 19 0 .93 2 .789-5 .343 1 .323CommonSMTwithPad&Heatsink 19 .8 38 2 .73 0 .628-2 .529 1 .869
FlippedOverwithHeatsink 23 .9 52 4 .12 0 .801-1 .726 2 .637
AllvaluesinthisSectionaretheresultofactualtestsunderlaboratoryconditionsandshouldprovideanindicationofthecapabilitiesofseveraldesignvariants .ThebehavioroftheseICsmaydifferunderdifferentdesignandopera-tionconditions .
High-Power Heat SinkingSincetheSA306-IHZisdesignedforhigherpowerapplications,itisalsonecessarytodetermineheatsinkingfac-torsthatallowforhigherpowerdissipation .Becauseoftheconcentrationofheatasaresultofpowerdensity,itisimportanttouseheatsinktypesthatprovideshortthermalpaths .Forthisreasonlargeextrusionswithfinsonwidecentershavenotbeenincludedinthisevaluation .Dissipationcapacitywithtwotypesofaluminumextrusionswereevaluated .TheHS33isasmallheatsink,0 .4"x0 .4"x1 .5",thathasfourfinson0 .118-inchcenters .ThisconfigurationplacesallfourfinsdirectlyundertheheatslugoftheSA306-IHZpackage .TheHS33heatsinkisshowninFigure20 .ThisheatsinkisusedontheApexMicrotech-nologyDB64RevaluationboardfortheSA306-IHZ .Thesecondheatsink inFigure21 isapinconfigurationwithdimensionsof1"x2"x2" .Thepinsare0 .070" indiameteron0 .137"centers .Thishighlyeffectiveheatsinkprovidesmultipleheatpathsdirectlyunderthesilicon .Becauseofitssize,itiscapableofsafelydissipatingmuchhigherpowerlevelsthantheHS33 .Thetestset-upfortheHS33usedtheApexMicrotechnologyDB64Revaluationboardwithan8Ωresistiveload .Toincreasepower,theDCvoltageacrosstheboardandloadwereincreased .Thisset-updoesnotfullysimulatetheoperationofamotor .However,itdoesallowstabletemperaturestobeachieved,thusfacilitatingmeasurement .Thisset-upmetthegoalofallowingpowerdissipationanddietemperaturemeasurementswithvaryingheatsinks .
Figure 20. HS33 Finned Heatsink with SA306-IHZ Figure 21. Pin Heatsink with SA306-IHZ
AN50
12 AN50U
Table 2. Results of Thermal Testing
Configuration Orientation Convection Dissipated Power (W)
Output Power @ 85% Effi-
ciency (W)
Heatsink Temp MAX
(ºC)
Junction Temp MAX
(ºC)
Thermal Resis-tance (ºC/W)
HS33andPCB
Horizontal,HSdown Natural 7 .5 42 .5 139 145 16
HS33andPCB
Vertical,HSvertical Natural 9 51 138 146 13
HS33andPCB
Horizontal,HSdown Forced 17 96 .3 127 140 6 .8
PinHeatsink Horizontal,HSup Natural 16 90 .7 125 141 7 .3
PinHeatsink Horizontal,HSdown Forced 39 221 .0 79 113 2 .3
Fivedifferentthermalconfigurationsweretested,andtheresultsareshowninTable2 .Notethatconsistentwithrealworldapplications,thedifferencesintestset-upandmeasurementtechniquesbetweenthistestandtheprevioussectionproducedifferenttestresultsandpowercapabilities .Thisistobeexpectedandshowsthatdesignersmusttakeintoaccounttheirspecificoperatingenvironmentwhenevaluatingthermalperformance .ThreerowsofHS33dataareshowninTable2 .Thefirsttwousedconvectioncoolingonly .Asonemightassume,placingtheheatsinkinahorizontalpositiondoesnotproduceaseffectiveacoolingsurfaceasplacingtheheatsinkvertically .Withaverticalheatsinkunderconvectionconditionstheheatsinkdissipates9W,allowing50Wofmotorpowerata+140°Cjunctiontemperature .Thermalresistanceresultswiththeverticalheatsinkmeasured13°C/Wjunctiontoair .The thirdHS33testwasperformedusingasmall fanblowingacross theboard .Theobjectwas tosimulateanenclosedhousingwithafanprovidingoutsideair,similartoaPC .Inthiscase,dissipationimprovedto17Wandallowingalmost100Watthemotorat85%efficiency .Thermalresistancejunction-to-casealsoimproveddramati-callyto6 .8°C/W .Subsequent testingwith this configuration suggests that use of a small fan, in this case a 1" Sunon unit (PNGM0502PFV1-8,similartoMPUorgraphicschipFAN),directedontotheHS33,allowsheatsinkdissipationinex-cessof21Wandsuggestingmotorpowerofapproximately120W .Undertheseconditions,dietemperatureshouldnotexceed+140°C .For full-power applications, the pin heatsink was tested . The pin heatsink was tested under both convectionandforced-airconditions .ThetestboardandfancanbeseeninFigure22 .Thefanusedwasa2"Sunon(PNKDE1205PHV2)capableof595linearfeetperminuteofairflow .Theretainingscrewsforthefanalsoholdtheheatsinkandthedeviceinplaceontheboard .ThetestconfigurationforthepinheatsinkusedamodifiedPCBlayoutanda4Ωresistiveload .Undernormalconvectionconditions,thisheatsinkwasabletodissipate16Wofpower,allowingmotorpowerof91W,similartotheHS33withairflow .However,whenusingforcedairwiththisheatsink,powerdissipationwithintheheatsinkincreasedtoalmost40W,allowingforgreaterthan220Wofpowertothemotor .Inaddition,thejunctiontemperaturedroppedto+113°C,sug-gestingthisisahighreliabilityconfigurationwithroomforincreasedpoweroutput .The junction to air thermal resistance also improved dramatically,measuring2 .3°C/W .Withsomeincreaseindietemperatureandawellde-signedsystem,thepinheatsinkinaforcedairconfigurationwillallowthefull48Wand5Aratingofthedevice .Useofaheatsinkdoesincreasesystemcost .Insomecases,thedesignermayfindthatasmallamountofairflowacrossanHS33-typeheatsinkpro-videssufficientdissipationandlowercostsversusalargerheatsink .How-ever,forfullpowerdissipation,useofalargeheatsinkwithforcedairmaybenecessary . Figure 22. Pin heatsink and test
board with fan attached
AN50
AN50U 13
Power Dissipation DeratingToprovidehigh-reliabilityoperation,thedietemperaturemustbekepttoasafelevel .Thedesignermustconsidertotalpower,heatsinkcapabilityandambienttemperatureinordertomakeappropriatesystemchoices .ThegraphinFigure23showsderatingcurvesforpower .Curvesaregivenforloadpowerversusheatsinkandambienttem-peratures .Inaddition,curvesaregivenforsingle-sidedanddoublelayerPCBs .Figure23alsoshowsthatbelow+25°CtheSA306-IHZcanoperateabove300W,assumingdietemperaturesareheldtoareliablelevel .Above+30°Cimprovedheatsinkingmustbeemployedorthedevicemayneedtobede-rated .Again,actualpowercapabilityisafunctionofoperatingvoltage,efficiency,ambienttemperatureandheatsinkcapability .Actualderatingwillvarybasedonthesefactors .Itshouldalsobenotedthatthederatingofheatsinksthemselveschangewithtemperatureandthereforewithpowerdissipation .AsshowninFigure24fortheHS33,bothairflowandambienttemperatureplayaroleinaccuratelymodelingthedissipationcapabilityoftheheatsink .
ConclusionApplicationsvarywidelyandvarious thermal techniquesareavail-able tomatch the required performance .The size and orientationoftheheatsinkmustbeselectedtomanagetheaveragepowerdis-sipationoftheIC .StandardPCBmountingtechniquesenablethesedevicestodissipateasmuchas9W .Theuseofaheatpadorthepatent-pending mounting technique shown in Figure 20, with theSA306-IHZinvertedandsuspendedthroughacutoutinthePCB,isadequateforpowerdissipationexceeding20W .Infreeair,mountingthePCBperpendiculartotheground,sothattheheatedairflowsupwardalongthechannelsofthefins,canprovideimprovedcooling .Inapplicationsinwhichhigherpowerdissipationor lowerjunctionorcasetemperaturesarerequired,alargerheat-sink or circulated air can significantly improve performance .A pinheatsink can successfully dissipate the thermal energy generatedwhendrivingmotors inexcessof200W .Byusing the techniquesinthisApplicationNote,theSA57-IHZandSA306-IHZcanprovidelong-term,reliablemotorcontrolinaverycompactpackage .
References1 . SA57-IHZ Pulse Width Modulation AmplifierDataSheet,www .apexanalog .com2 . SA306-IHZ Pulse Width Modulation AmplifierDataSheet,www .apexanalog .com3 . 3-Phase Switching AmplifierApplicationNoteSA306-IHZ,AN46,www .apexanalog .com
SA306-IHZ Output Power Dissipation Derating
0
50
100
150
200
250
300
350
0 20 40 60 80 100 120 140Ambient Temperature, Ta (°C)
Load
Pow
er, P
(W)
HS33 and PCB Horizontal/HSdown - Natural HS33 and PCB Vertical/HSvertical - Natural HS33 and PCB Horizontal/HSdown - Forced
PIN Heatsink Horizontal/HSdown - Forced
Note: Careful consideration of operating current isrequired so not to exceed maximum wire temp of +150° C.
0
50
100
150
200
250
300
350HS33 and PCB Horizontal/HSdown - Natural HS33 and PCB Vertical/HSvertical - Natural HS33 and PCB Horizontal/HSdown - Forced PIN Heatsink Horizontal/HS up - Natural PIN Heatsink Horizontal/HSdown - Forced Typical SMT device on a Double-Sided BoardTypical SMT device on a Single-Sided Board
THE
RM
AL
RE
SIS
TAN
CE
(°C
/W)
AIR FLOW (LFM)200 1000800600400
0.00
20.00
15.00
10.00
5.00
1.0 5.14.13.02.0AIR FLOW (m/s)
Figure 23. Load power derating curves for ambient temperature, Ta (°C)
Figure 24. Heatsink thermal resistance versus air flow
AN50
14 AN50U
Appendix A – Derivation of Maximum Power and Thermal Dynamics Values for PCB Based TestsSection A.1 Result for Common SMT Mounting with Heatsink in Low-Power Applications
ThetotalthermalresistanceofthecommonSMTmodelforaSA306-IHZis4 .98K/W(Kelvinperwatt) .Tocalculatethemaximumoutputpowerforthismountingtechniquewithoutspecificvaluesforvoltageorcurrent,wehavetotransformtheequation:
(12)Where: T0=SA306-IHZorSA57-IHZjunctiontemperature T2=ambientairtemperature PE=electricaloutputpower
TheplotsinFigure7denoteavalueof+136°Catanambienttemperatureof+27°Cwithathermalresistanceofapproximately5 .343K/W .Thedifferenceisduetothefactthatthefactorincludesthethermalresistanceintotheambientairandisthereforeacombinedvaluefor(αA)-1+Rth .WhenweusethevalueforthethermalresistanceofthePICtailTMPlusTestBoardtocalculatethemaximumoutputpowerforanapplicationcoveringthewholeindustrialambienttemperaturerangeupto+85°C,themaximumcon-tinuousoutputpowerisapproximately9W:
(13)
Where: T0=SA306-IHZorSA57-IHZjunctiontemperature T2=ambientairtemperature RT=totalthermalconductivity PMAX=MAXelectricaloutputpower
ShowninFigure12isthetemperaturecharacteristicofthegroundplanefromtheambienttothemaximumtem-perature,whenthemotorisdrivencontinuouslyatamaximumpowerof9W .ForlatercomparisonsthefocusisonthetransferratioΔT30/Δt30andΔT90/Δt90,describedbyaquotientKfortheslewratefromthecoldstateto30%and90%,respectively,ofthemaximumtemperature .Theslewratequotientkisanindicationforthequalityofthedynamicbehaviourofthethermalsystem:
(14a)
(14b)Where:
k=slewratequotientinKelvinpersecond Δθ=temperaturedifferenceinKelvin Δt=durationinseconds T0=temperatureattimet0 T1=temperatureattimet1
T0 - T2 = ( + Rth) • RDS(ON) • IC21
αA
T0 - T2 = ( + Rth) • PE
1αA
PMAX =T0 - T2
Rt
PMAX = = 9.4W135°C - 85°C
5.343 KW
k = = ∆θ T1 - T0∆t t1 - t0
k30 = = 1.31754.5°C - 26.8°C21 sec
Ksec
k90 = = 0.988109.7°C - 26.8°C84 sec
Ksec
AN50
AN50U 15
Section A.2 SMT Mounting with a Thermal Pad and Heatsink for Mid-Range Power Applications
Thefirstorderapproximationofthethermalmodelgivesathermalresistanceof2 .678K/W .Thefollowingequationisusedtoverifytherealvalueofthecompletesystem:
(15)
Where:T0=SA306-IHZorSA57-IHZjunctiontemperatureT2=ambientairtemperaturePE=electricaloutputpowerRt=totalthermalconductivity
Nextistofindthemaximumpowerratingtocoverthetotalindustrialrangeforambienttemperaturesupto+85°Catamaximumdietemperatureof+135°C .
(16)
Where:T0=SA306-IHZorSA57-IHZjunctiontemperatureT2=ambientairtemperatureRt=totalthermalconductivityPMAX=Max .electricaloutputpower
ThechartinFigure12showstheimprovementsofthethermaldynamics .Theslewratequotientsk30andk90are:
(17a)
(17b)
Where:k=slewratequotientinK/sΔθ=temperaturedifferenceinKelvinΔt=durationinsecondsT0=temperatureattimet0T1=temperatureattimet1
= ( + Rth)1αA
T0 - T2 = ( + Rth) • PE
1αA
T0 - T2PE
Rt = = 2.529155°C - 26°C51W
KW
PMAX =T0 - T2
Rt
PMAX = = 19.8W135°C - 85°C
2.529 KW
k = = ∆θ T1 - T0∆t t1 - t0
k30 = = 1.93855.8°C - 26.8°C15 sec
Ksec
k90 = = 1.407114.7°C - 26.8°C63 sec
Ksec
AN50
16 AN50U
Section A.3 Flipped Over SMT Mounting with Heatsink for High-Power Applications
Thefollowingequationsareusedtocalculatetheestimatedmaximumoutputpowerforambienttemperaturesof+85°C:
(18)
Where:T0=SA306-IHZ/SA57-IHZjunctiontemperatureT2=ambientairtemperatureRt=totalthermalconductivityPMAX=MAXelectricaloutputpower
Usingthismountingtechnique,thefollowingvaluesareobtainedfork30andk90:
(19a) (19b)Where:k=slewratequotientinK/sΔθ=temperaturedifferenceinKelvinΔt=durationinsecondsT0=temperatureattimet0T1=temperatureattimet1
k = = ∆θ T1 - T0∆t t1 - t0
k30 = = 2.63858.5°C - 26.8°C12 sec
Ksec
k90 = = 1.792121.8°C - 26.8°C53 sec
Ksec
PMAX =T0 - T2
Rt
PMAX = = 28.97W135°C - 85°C
2.096 KW
= ( + Rth)1αA
T0 - T2PE
Rt = = 2.096135°C - 26°C52W
KW
NEED TECHNICAL HELP? CONTACT APEX SUPPORT!ForallApexMicrotechnologyproductquestionsandinquiries,calltollfree800-546-2739inNorthAmerica .Forinquiriesviaemail,pleasecontactapex .support@apexanalog .com .InternationalcustomerscanalsorequestsupportbycontactingtheirlocalApexMicrotechnologySalesRepresentative .Tofindtheonenearesttoyou,gotowww .apexanalog .comIMPORTANTNOTICE
ApexMicrotechnology,Inc .hasmadeeveryefforttoinsuretheaccuracyofthecontentcontainedinthisdocument .However,theinformationissubjecttochangewithoutnoticeandisprovided"ASIS"withoutwarrantyofanykind(expressedorimplied) .ApexMicrotechnologyreservestherighttomakechangeswithoutfurthernoticetoanyspecificationsorproductsmentionedhereintoimprovereliability .ThisdocumentisthepropertyofApexMicrotechnologyandbyfurnishingthisinforma-tion,ApexMicrotechnologygrantsnolicense,expressedorimpliedunderanypatents,maskworkrights,copyrights,trademarks,tradesecretsorotherintellectualpropertyrights .ApexMicrotechnologyownsthecopyrightsassociatedwiththeinformationcontainedhereinandgivesconsentforcopiestobemadeoftheinforma-tiononlyforusewithinyourorganizationwithrespecttoApexMicrotechnologyintegratedcircuitsorotherproductsofApexMicrotechnology .Thisconsentdoesnotextendtoothercopyingsuchascopyingforgeneraldistribution,advertisingorpromotionalpurposes,orforcreatinganyworkforresale .
APEXMICROTECHNOLOGYPRODUCTSARENOTDESIGNED,AUTHORIZEDORWARRANTEDTOBESUITABLEFORUSEINPRODUCTSUSEDFORLIFESUPPORT,AUTOMOTIVESAFETY,SECURITYDEVICES,OROTHERCRITICALAPPLICATIONS .PRODUCTSINSUCHAPPLICATIONSAREUNDER-STOODTOBEFULLYATTHECUSTOMERORTHECUSTOMER’SRISK .
ApexMicrotechnology,ApexandApexPrecisionPoweraretrademarksofApexMicrotechnolgy,Inc .Allothercorporatenamesnotedhereinmaybetrademarksoftheirrespectiveholders .
Copyright © Apex Microtechnology, Inc. 2012(All Rights Reserved)www.apexanalog.com OCT 2012
AN50U REVB