TPS72518KTT资料

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TPS72515,TPS72516TPS72518,TPS72525

SLVS341D–MAY2002–REVISEDMARCH2004LOWINPUTVOLTAGE,1-ALOW-DROPOUTLINEARREGULATORSWITHSUPERVISOR

FEATURES

••

1-AOutputCurrent

Availablein1.5-V,1.6-V,1.8-V,2.5-VFixed-OutputandAdjustableVersions(1.2-Vto5.5-V)

InputVoltageDownto1.8V

Low170-mVDropoutVoltageat1A(TPS72525)

StableWithAnyType/ValueOutputCapacitorIntegratedSupervisor(SVS)With50-msRESETDelayTime

Low210-µAGroundCurrentatFullLoad(TPS72525)

Lessthan1-µAStandbyCurrent

±2%OutputVoltageToleranceOverLine,Load,andTemperature(-40°Cto125°C)IntegratedUVLO

ThermalandOvercurrentProtection

5-LeadSOT223-5orDDPAKand8-PinSOP(TPS72501only)SurfaceMountPackage

DESCRIPTION

TheTPS725xxfamilyof1-Alow-dropout(LDO)linearregulatorshasfixedvoltageoptionsavailablethatarecommonlyusedtopowerthelatestDSPs,FPGAs,andmicrocontrollers.Anadjustableoptionrangingfrom1.22Vto5.5Visalsoavailable.TheintegratedsupervisorycircuitryprovidesanactivelowRESETsignalwhentheoutputfallsoutofregulation.Thenocapacitor/anycapacitorfeatureallowsthecustomertotailoroutputtransientperformanceasneeded.Therefore,comparedtootherregulatorscapableofprovidingthesameoutputcurrent,thisfamilyofregulatorscanprovideastand-alonepowersupplysolutionorapostregulatorforaswitchmodepowersupply.

Theseregulatorsareidealforhighercurrentappli-cations.Thefamilyoperatesoverawiderangeofinputvoltages(1.8Vto6V)andhasverylowdropout(170mVat1-A).

Groundcurrentistypically210µAatfullloadanddropstolessthan80µAatnoload.Standbycurrentislessthan1µA.

EachregulatoroptionisavailableineitheraSOT223-5,D(TPS72501only),orDDPAKpackage.Withalowinputvoltageandproperlyheatsinkedpackage,theregulatordissipatesmorepowerandachieveshigherefficienciesthansimilarregulatorsrequiring2.5Vormoreminimuminputvoltageandhigherquiescentcurrents.Thesefeaturesmakeitaviablepowersupplysolutionforportable,bat-tery-poweredequipment.

D PACKAGE(TOP VIEW)

••••••••••

APPLICATIONS

•••••

PCICardsModemBanksTelecomBoards

DSP,FPGA,andMicroprocessorPowerSupplies

Portable,Battery-PoweredApplications

DCQ PACKAGESOT223-5(TOP VIEW)

ENABLEINGNDOUTRESET/FB12345

12345

KTT PACKAGE

DDPAK(TOP VIEW)

OUTFBGNDNC

1234

8765

INGNDGNDENABLE

ENABLEINGNDOUTRESET/FBNC − No internal connection

NOTE:TPS72501replacesRESETwithFB.TabisGNDfortheDCKandKTTpackages.

Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.

PRODUCTIONDATAinformationiscurrentasofpublicationdate.ProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.Productionprocessingdoesnotnecessarilyincludetestingofallparameters.

Copyright©2002–2004,TexasInstrumentsIncorporated

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Thesedeviceshavelimitedbuilt-inESDprotection.TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.

DESCRIPTION(CONTINUED)

Althoughanoutputcapacitorisnotrequiredforstability,transientresponseandoutputnoiseareimprovedwitha10-µFoutputcapacitor.

Unlikesomeregulatorsthathaveaminimumcurrentrequirement,theTPS725familyisstablewithnooutputloadcurrent.Thelownoisecapabilityofthisfamily,coupledwithitshighcurrentoperationandeaseofpowerdissipation,makeitidealfortelecomboards,modembanks,andothernoise-sensitiveapplications.

ORDERINGINFORMATION

TJVOLTAGE(1)Adjustable(1.2Vto5V)1.5V-40°Cto125°C1.6V1.8V2.5V(1)(2)(3)(4)

SOT223-5(2)TPS72501DCQTPS72515DCQTPS72516DCQTPS72518DCQTPS72525DCQSYMBOLPS72501PS72515PS72516PS72518PS72525DDPAK(3)TPS72501KTTTPS72515KTTTPS72516KTTTPS72518KTTTPS72525KTTD(4)TPS72501D————SYMBOLTPS72501TPS72515TPS72516TPS72518TPS72525Othervoltageoptionsareavailableuponrequestfromthemanufacturer.

Toorderatapedandreeledpart,addthesuffixRtothepartnumber(e.g.,TPS72501DCQR).

Toordera50-piecereel,addthesuffixT(e.g.,TPS72501KTTT);toordera500-piecereel,addthesuffixR(e.g.,TPS72501KTTR).Toorderatapedandreeledpart,addthesuffixRorT(2500or500)tothepartnumber(e.g.TPS72501DR)

ABSOLUTEMAXIMUMRATINGS

overoperatingfree-airtemperaturerangeunlessotherwisenoted(1)

UNITInputvoltage,VI(2)-0.3to7-0.3toVI+0.362-50to150150-65to150VVVkV°C°C°CVoltagerangeatEN,FBVoltageonOUT,RESETESDrating,HBMContinuoustotalpowerdissipationOperatingjunctiontemperaturerange,TJMaximumjunctiontemperaturerange,TJStoragetemperature,Tstg(1)(2)

SeeDissipationRatingsTableStressesbeyondthoselistedunderabsolutemaximumratingsmaycausepermanentdamagetothedevice.Thesearestressratingsonly,andfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderrecommendedoperatingconditionsisnotimplied.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.Allvoltagevaluesarewithrespecttonetworkgroundterminal.

RECOMMENDEDOPERATINGCONDITIONS

MINNOMMAXUNITInputvoltage,VI(1)1.80-4061125VA°CContinuousoutputcurrent,IOOperatingjunctiontemperature,TJ(1)

MinimumVI=VO(nom)+VDO.

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PACKAGEDISSIPATIONRATINGS

PACKAGEDDPAKSOT223D-8(1)(2)

BOARDHighK(1)LowK(2)HighK(1)RθJC2°C/W15°C/W39.4°C/WRθJA23°C/W53°C/W55°C/WTheJEDEChigh-K(2s2p)boarddesignusedtoderivethisdatawasa3-inchx3-inch(7.5-cmx7.5-cm),multilayerboardwith1ounceinternalpowerandgroundplanesand2ouncecoppertracesontopandbottomoftheboard.

TheJEDEClow-K(1s)boarddesignusedtoderivethisdatawasa3-inchx3-inch(7.5-cmx7.5-cm),two-layerboardwith2ouncecoppertracesontopoftheboard.

ELECTRICALCHARACTERISTICS

overrecommendedoperatingfree-airtemperaturerangeVI=VO(typ)+1V,IO=1mA,EN=IN,Co=1µF,Ci=1µF(unlessotherwisenoted)

PARAMETERBandgapvoltagereferenceTPS72501AdjustableTPS72515VOOutputvoltageTPS72516TPS72518TPS72525IGroundcurrentStandbycurrentVnPSRROutputnoisevoltageRipplerejectionCurrentlimit(2)Outputvoltagelineregulation(∆VO/VO)(3)OutputvoltageloadregulationVIHVILIII(FB)ENhighlevelinput(2)ENlowlevelinput(2)ENinputcurrentFeedbackcurrentUVLOthresholdUVLOhysteresisUVLOdeglitchUVLOdelay(1)(2)(3)

EN=0VorVITPS72501VCCrisingTJ=25°C,VCCrisingTJ=25°C,VCCrisingTJ=25°C,VCCrisingV(FB)=1.22-1001.451.575010100VO+1VTestconditionincludesoutputvoltageVO=VO-15%andpulseduration=10ms.VImin=(VO+1)or1.8Vwhicheverisgreater.

Lineregulation(mV)+ǒ%ńVǓ

V

O

ǒ5.5V*VIminǓ

100 1000

3

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ELECTRICALCHARACTERISTICS(continued)

overrecommendedoperatingfree-airtemperaturerangeVI=VO(typ)+1V,IO=1mA,EN=IN,Co=1µF,Ci=1µF(unlessotherwisenoted)

PARAMETERTPS72525VDODropoutvoltageTPS72518MinimuminputvoltageforvalidRESETTripthresholdvoltageHysteresisvoltageRESETt(RESET)delaytimeRisingedgedeglitchOutputlowvoltage(at700µA)Leakagecurrent(4)

-0.325(4)(4)TESTCONDITIONSIO=1AIO=1AIO=1AIO=1ATJ=25°CTJ=25°CMINTYP170MAX280UNIT2103201.390931050100.41007596mVV%VOmVmsµsVnADropoutvoltageisdefinedasthedifferentialvoltagebetweenVOandVIwhenVOdrops100mVbelowthevaluemeasuredwithVI=VO+1V.

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FUNCTIONALBLOCKDIAGRAM—ADJUSTABLEVERSION

TPS72501INEN

1.220VrefGND

CurrentLimit/ThermalProtectionOUT

FB

FUNCTIONALBLOCKDIAGRAM—FIXEDVERSION

TPS72515/16/18/25

INEN1.220VrefGND

CurrentLimit/ThermalProtectionOUT

DeglitchandDelay0.93󰀀× VrefRESETTERMINALFUNCTIONS

TERMINALNAMEENABLEFBGNDINRESET/FBNO.D523,6,78—325IO/INO.DCQ&KTT1I/ODESCRIPTIONIEnableinputFeedbackGroundInputsupplyvoltageThisterminalisthefeedbackpointfortheadjustableoptionTPS72501.Forallotheroptions,thisterminalistheRESEToutputterminal.Whenusedwithapullupresistor,thisopen-drainoutputprovidestheactivelowRESETsignalwhentheregulatoroutputvoltagedropsmorethan5%belowitsnominaloutputvoltage.TheRESETdelaytimeistypically50ms.NoconnectionRegulatedoutputvoltageNCOUT41—4O5

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RESETTIMINGDIAGRAM

IN

VRES(see Note A)OUTThresholdVoltageVIT–(see Note B)VIT–(see Note B)VIT+(see Note B)VIT+(see Note B)VRESttRESETOutput50 msDelay50 msDelayOutputUndefinedOutputUndefinedtNOTES:A.VRES is the minimum input voltage for a valid RESET. The symbol VRES is not currently listed within EIA or JEDEC standards for

semiconductor symbology.

B.VIT –Trip voltage is typically 7% lower than the output voltage (93%VO) VIT– to VIT+ is the hysteresis voltage.

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TYPICALCHARACTERISTICS

TPS72518

OUTPUTVOLTAGE

vs

OUTPUTCURRENT

1.80151.801VO− Output Voltage − VVI = 2.8 VCo = 1 µFTJ = 25°󰀀C1.805VI = 2.8 VCo = 1 µFVO− Output Voltage − V1.800IO = 0 mAGround Current − µA200TPS72518

OUTPUTVOLTAGE

vs

JUNCTIONTEMPERATURE

250TPS72518

GROUNDCURRENT

vs

JUNCTIONTEMPERATURE

VI = 2.8 VCo = 1 µFTJ = 25°󰀀CIO = 1 A1.80051.81.79951.7991.798500.20.40.60.81IO − Output Current − A

1501.795100IO = 0 mA1.790IO = 1 A501.785−40−25−105203550658095110125TJ − Junction Temperature − °C

0−40−25−105203550658095110125TJ − Junction Temperature − °C

Figure1.TPS72518

GROUNDCURRENT

vs

OUTPUTCURRENT

200175Ground Current − µA15012510075502500.01

VDO− Dropout Voltage − mV300Figure2.

TPS72525

DCDROPOUTVOLTAGE

vs

OUTPUTCURRENT

300VO = 2.5 V (nom)VDO− Dropout Voltage − mV250200150100500TJ = −40°CTJ = 25°CTJ = 125°C250200150100500−40−25−105Figure3.

TPS72518

DROPOUTVOLTAGE

vs

JUNCTIONTEMPERATURE

VO = 1.7 VCo = 1 µFIO = 1 AIO = 10 mA2035506580951101250.1110100100000.2IO − Output Current − mA

0.40.60.8IO − Output Current − A

1TJ − Junction Temperature − °C

Figure4.

MINIMUMREQUIREDINPUTVOLTAGE

vs

OUTPUTVOLTAGE

VI− Input Voltage − V4.5VI− Minimum Required Input Voltage − V3.8Figure5.Figure6.

TPS72518

LINETRANSIENTRESPONSE

Output Voltage − mV∆VO− Change inIO = 1 ACo = 10 µF1000−100TPS72518

LOADTRANSIENTRESPONSE

VO = 2.8 VCo = 10 µFCi = 1 µF43.5TJ = 25°CTJ = 125°C2.83VO− Output Voltage − mVIO− Output Current − A2.5TJ = −40°C21.51.522.533.544.5VO − Output Voltage − V

1000−100050100150200250300350400450500t − Time − µs

10.5005101520253035404550t − Time − µs

Figure7.Figure8.Figure9.

7

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TYPICALCHARACTERISTICS(continued)

TPS72518OUTPUTVOLTAGE,

ENABLEVOLTAGE

vs

TIME(START-UP)

Enable Voltage − VVI− Input Voltage − V32102VO− Output Voltage − V1.510.50020406080100120140160180200t − Time − µs

VI = 2.8 VIO = 1 ACo = 10 µF543210VOTPS72518

LOADTRASIENTRESPONSE

Output Voltage − mV∆VO− Change in1000−100VI = 2.8 VCo = 1 µFCI = 1 µFTPS72518

POWERUP/POWERDOWN

RL = 1.8 ΩCo = 1 µFCi = 1 µFVII − Output Current − AO10.500510152025303540t − Time − µs

4550V − Output Voltage − VO01002003004005006007008009001000t − Time − µs

Figure10.

TPS72518OUTPUTSPECTRAL

NOISEDENSITY

vs

FREQUENCY

Hz3.532.52IO = 1 A1.510.50101001 k10 kf − Frequency − Hz

100 kIO = 1 mAVI = 2.8 VCo = 10 µFFigure11.Figure12.TPS72518

RIPPLEREJECTION

vs

FREQUENCY

10090VI= 2.8 V,VO = 1.8 V,CO = 10 µFOUTPUTIMPEDANCE

vs

FREQUENCY

10IO = 1 A1IO = 1 mARipple Rejection − dBOutput Spectral Noise Density − µV/Zo− Output Impedance −Ω8070605040302010010 µF / 1 A10 µF / 1mA0.10.01010VI = 2.8 VCo = 10 µFTJ = 25°󰀀C1001 k10 k100 k1 M101001 k10 k100 k1 Mf − Frequency − Hz

f − Frequency − Hz

Figure13.CURRENTLIMIT

vs

INPUTVOLTAGE

200019001800Current Limit − A170016001500140013001200110010001.522.533.544.555.50012TJ = 25°CTJ = −40°CTJ = 125°CGround Current −µA600500400300200Figure14.

TPS72515GROUNDCURRENT

vs

INPUTVOLTAGE

300250200150100Figure15.DROPOUTVOLTAGE

vs

INPUTVOLTAGE

TJ = 125°CTJ = 25°CI = 1 AVDO− Dropout Voltage − mVI = 0 A100TJ = −40°C50034561.52VI − Input voltage − VVI − Input Voltage − V

2.533.544.5VI − Input Voltage − V

55.5Figure16.Figure17.Figure18.

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APPLICATIONINFORMATION

TheTPS725xxfamilyoflow-dropout(LDO)regulatorshasnumerousfeaturesthatmakeitapplicabletoawiderangeofapplications.Thefamilyoperateswithverylowinputvoltage(≥1.8V)andlowdropoutvoltage(typically200mVatfullload),makingitanefficientstand-alonepowersupplyorpostregulatorforbatteryorswitchmodepowersupplies.BoththeactivelowRESETand1-AoutputcurrentmaketheTPS725xxfamilyidealforpoweringprocessorandFPGAsupplies.TheTPS725xxfamilyalsohaslowoutputnoise(typically150µVRMSwith10-µFoutputcapacitor),makingitidealforuseintelecomequipment.

ExternalCapacitorRequirements

A1-µForlargerceramicinputbypasscapacitor,connectedbetweenINandGNDandlocatedclosetotheTPS725xx,isrequiredforstability.Toimprovetransientresponse,noiserejection,andripplerejection,anadditional10-µForlarger,lowESRcapacitorisrecommended.Ahigher-value,lowESRinputcapacitormaybenecessaryiflarge,fast-rise-timeloadtransientsareanticipatedandthedeviceislocatedseveralinchesfromthepowersource,especiallyiftheminimuminputvoltageof1.8Visused.

Althoughanoutputcapacitorisnotrequiredforstability,transientresponseandoutputnoiseareimprovedwitha10-µFoutputcapacitor.

ProgrammingtheTPS72501AdjustableLDORegulator

TheoutputvoltageoftheTPS72501adjustableregulatorisprogrammedusinganexternalresistordividerasshowninFigure19.Theoutputvoltageiscalculatedusing:

VO+V

1)R1refR2

ǒǓ(1)

Where:

•VFB=VREF=1.22Vtypical(seetheelectricalcharacteristicsforVREFrange)

ResistorsR1andR2shouldbechosenforapproximately10-µAdividercurrent.Lowervalueresistorsoffernoinherentadvantageandwastemorepower.HighervaluesshouldbeavoidedasleakagecurrentsatFBincreasetheoutputvoltageerror.TherecommendeddesignprocedureistochooseR2=120kΩtosetthedividercurrentat10µAandthencalculateR1using:

R1+

ǒ

O*1Vref

V

Ǔ

R2

(2)

TPS72501OUTPUT VOLTAGEPROGRAMMING GUIDE(Standard 1% Resistor Values)

PROGRAMVOLTAGE

VI1 µF≥ 1.3 V≤󰀀0.4 VINR1 (KΩ)R2 (kΩ)VOLTAGE56.2127196205

118121115105

1.8012.5003.2993.602

ACTUAL

ENOUTR1FBGND1.22 VR2VOCo

1.8 V2.5 V3.3 V3.6 V

Figure19.TPS72501AdjustableLDORegulatorProgramming

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APPLICATIONINFORMATION(continued)

TheTPS725xxpasselementhasabuilt-inbackdiodethatsafelyconductsreversecurrentwhentheinputvoltagedropsbelowtheoutputvoltage(e.g.,duringpowerdown).Currentisconductedfromtheoutputtotheinputandisnotinternallylimited.Ifextendedreversevoltageisanticipated,externallimitingmightbeappropriate.

TheTPS725xxalsofeaturesinternalcurrentlimitingandthermalprotection.Duringnormaloperation,theTPS725xxlimitsoutputcurrenttoapproximately1.6A.Whencurrentlimitingengages,theoutputvoltagescalesbacklinearlyuntiltheovercurrentconditionends.Whilecurrentlimitingisdesignedtopreventgrossdevicefailure,careshouldbetakennottoexceedthepowerdissipationratingsofthepackage.Ifthetemperatureofthedeviceexceeds165°C,thermal-protectioncircuitryshutsitdown.Oncethedevicehascooleddowntobelow145°C,regulatoroperationresumes.

THERMALINFORMATION

TheamountofheatthatanLDOlinearregulatorgeneratesisdirectlyproportionaltotheamountofpoweritdissipatesduringoperation.Allintegratedcircuitshaveamaximumallowablejunctiontemperature(TJmax)abovewhichnormaloperationisnotassured.Asystemdesignermustdesigntheoperatingenvironmentsothattheoperatingjunctiontemperature(TJ)doesnotexceedthemaximumjunctiontemperature(TJmax).Thetwomainenvironmentalvariablesthatadesignercanusetoimprovethermalperformanceareairflowandexternalheatsinks.Thepurposeofthisinformationistoaidthedesignerindeterminingtheproperoperatingenvironmentforalinearregulatorthatisoperatingataspecificpowerlevel.

Ingeneral,themaximumexpectedpower(PD(max))consumedbyalinearregulatoriscomputedas:

Pmax+V*V I)VxIDI(avg)O(avg)O(avg)I(avg)(Q)

ǒ

Ǔ

(3)

Where:

•VI(avg)istheaverageinputvoltage.•VO(avg)istheaverageoutputvoltage.•IO(avg)istheaverageoutputcurrent.•I(Q)isthequiescentcurrent.

FormostTILDOregulators,thequiescentcurrentisinsignificantcomparedtotheaverageoutputcurrent;therefore,thetermVI(avg)xI(Q)canbeneglected.Theoperatingjunctiontemperatureiscomputedbyaddingtheambienttemperature(TA)andtheincreaseintemperatureduetotheregulator'spowerdissipation.Thetemperatureriseiscomputedbymultiplyingthemaximumexpectedpowerdissipationbythesumofthethermalresistancesbetweenthejunctionandthecase(RθJC),thecasetoheatsink(RθCS),andtheheatsinktoambient(RθSA).Thermalresistancesaremeasuresofhoweffectivelyanobjectdissipatesheat.Typically,thelargerthedevice,themoresurfaceareaavailableforpowerdissipationandthelowertheobject'sthermalresistance.Figure20illustratesthesethermalresistancesfor(a)aSOT223packagemountedinaJEDEClow-Kboard,and(b)aDDPAKpackagemountedonaJEDEChigh-Kboard.

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THERMALINFORMATION(continued)

A

CIRCUIT BOARD COPPER AREA

CBA

RθJC

BRθCS

CRθSA

DDPAK Package

(b)

CTCTJ

ABSOT223 Package

(a)

TA

Figure20.ThermalResistances

Equation4summarizesthecomputation:

TJ

+T)PDmaxxR)R)R

AθJCθCSθSA

ǒ

Ǔ

(4)

TheRθJCisspecifictoeachregulatorasdeterminedbyitspackage,leadframe,anddiesizeprovidedinthe

regulator'sdatasheet.TheRθSAisafunctionofthetypeandsizeofheatsink.Forexample,blackbodyradiatortypeheatsinkscanhaveRθCSvaluesrangingfrom5°C/Wforverylargeheatsinksto50°C/Wforverysmallheatsinks.TheRθCSisafunctionofhowthepackageisattachedtotheheatsink.Forexample,ifathermalcompoundisusedtoattachaheatsinktoaSOT223package,RθCSof1°C/Wisreasonable.

Evenifnoexternalblackbodyradiatortypeheatsinkisattachedtothepackage,theboardonwhichtheregulatorismountedprovidessomeheatsinkingthroughthepinsolderconnections.Somepackages,liketheDDPAKandSOT223packages,useacopperplaneunderneaththepackageorthecircuitboard'sgroundplaneforadditionalheatsinkingtoimprovetheirthermalperformance.Computer-aidedthermalmodelingcanbeusedtocomputeveryaccurateapproximationsofanintegratedcircuit'sthermalperformanceindifferentoperatingenvironments(e.g.,differenttypesofcircuitboards,differenttypesandsizesofheatsinks,differentairflows,etc.).Usingthesemodels,thethreethermalresistancescanbecombinedintoonethermalresistancebetweenjunctionandambient(RθJA).ThisRθJAisvalidonlyforthespecificoperatingenvironmentusedinthecomputermodel.

Equation4simplifiesintoEquation5:T+T)PDmaxxRJAθJARearrangingEquation5givesEquation6:

T–T

R+JAθJAPmax

D

(5)

(6)

UsingEquation5andthecomputermodelgeneratedcurvesshowninFigure21andFigure24,adesignercanquicklycomputetherequiredheatsinkthermalresistance/boardareaforagivenambienttemperature,powerdissipation,andoperatingenvironment.

DDPAKPowerDissipation

TheDDPAKpackageprovidesaneffectivemeansofmanagingpowerdissipationinsurfacemountapplications.TheDDPAKpackagedimensionsareprovidedintheMechanicalDatasectionattheendofthedatasheet.TheadditionofacopperplanedirectlyunderneaththeDDPAKpackageenhancesthethermalperformanceofthepackage.

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THERMALINFORMATION(continued)

Toillustrate,theTPS72525inaDDPAKpackagewaschosen.Forthisexample,theaverageinputvoltageis5V,theoutputvoltageis2.5V,theaverageoutputcurrentis1A,theambienttemperature55°C,theairflowis150LFM,andtheoperatingenvironmentisthesameasdocumentedbelow.Neglectingthequiescentcurrent,themaximumaveragepoweris:

PDmax+(5*2.5)Vx1A+2.5W(7)SubstitutingTJmaxforTJintoEquation6givesEquation8:Rmax+(125*55)°Cń2.5W+28°CńWθJA

(8)

FromFigure21,DDPAKThermalResistancevsCopperHeatsinkArea,thegroundplaneneedstobe1cm2fortheparttodissipate2.5W.TheoperatingenvironmentusedinthecomputermodeltoconstructFigure21consistedofastandardJEDECHigh-Kboard(2S2P)witha1oz.internalcopperplaneandgroundplane.Thepackageissolderedtoa2oz.copperpad.Thepadistiedthroughthermalviastothe1oz.groundplane.Figure22showsthesideviewoftheoperatingenvironmentusedinthecomputermodel.

40No Air FlowRθJA− Thermal Resistance − °C/W35150 LFM30250 LFM2520150.1110Copper Heatsink Area − cm2

100Figure21.DDPAKThermalResistancevsCopperHeatsinkArea

2 oz. Copper Solder Padwith 25 Thermal Vias1 oz. CopperPower Plane1 oz. CopperGround PlaneThermal Vias, 0.3 mmDiameter, 1,5 mm Pitch

Figure22.DDPAKThermalResistance

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THERMALINFORMATION(continued)

FromthedatainFigure23andrearrangingEquation6,themaximumpowerdissipationforadifferentgroundplaneareaandaspecificambienttemperaturecanbecomputed.

TA = 55°CPD− Maximum Power Dissipation − WTJM− Maximum Junction Temperature − 125°C10054250 LFM150 LFM3No Air Flow210.1110Copper Heatsink Area − cm2

Figure23.MaximumPowerDissipationvsCopperHeatsinkArea

SOT223PowerDissipation

TheSOT223packageprovidesaneffectivemeansofmanagingpowerdissipationinsurfacemountapplications.TheSOT223packagedimensionsareprovidedintheMechanicalDatasectionattheendofthedatasheet.TheadditionofacopperplanedirectlyunderneaththeSOT223packageenhancesthethermalperformanceofthepackage.

Toillustrate,theTPS72525inaSOT223packagewaschosen.Forthisexample,theaverageinputvoltageis3.3V,theoutputvoltageis2.5V,theaverageoutputcurrentis1A,theambienttemperature55°C,noairflowispresent,andtheoperatingenvironmentisthesameasdocumentedbelow.Neglectingthequiescentcurrent,themaximumaveragepoweris:

PDmax+(3.3*2.5)Vx1A+800mW(9)SubstitutingTJmaxforTJintoEquation6givesEquation10:Rmax+(125*55)°Cń800mW+87.5°CńWθJA

(10)

FromFigure24,RΘJAvsPCBCopperArea,thegroundplaneneedstobe0.55in2fortheparttodissipate800mW.TheoperatingenvironmentusedtoconstructFigure24consistedofaboardwith1oz.copperplanes.Thepackageissolderedtoa1oz.copperpadonthetopoftheboard.Thepadistiedthroughthermalviastothe1oz.groundplane.

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TPS72515,TPS72516

TPS72518,TPS72525

SLVS341D–MAY2002–REVISEDMARCH2004

www.ti.com

THERMALINFORMATION(continued)

180RθJA− Thermal Resistance − °C/W1601401201008060402000.11PCB Copper Area − in2

10No Air FlowFigure24.SOT223ThermalResistancevsPCBAREA

FromthedatainFigure24andrearrangingEquation6,themaximumpowerdissipationforadifferentgroundplaneareaandaspecificambienttemperaturecanbecomputed(asshowninFigure25).6TA = 25°CPD− Maximum Power Dissipation − W544 in2 PCB Area30.5 in2 PCB Area2100255075100125150TA − Ambient Temperature − °C

Figure25.SOT223PowerDissipation

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