TPS72618KTT资料

TPS72615,TPS72616TPS72618,TPS72625

www.ti.comSLVS403C–MAY2002–REVISEDMARCH2004LOWINPUTVOLTAGE,1-ALOW-DROPOUTLINEARREGULATORSWITHSUPERVISOR

FEATURES

••

1-AOutputCurrent

Availablein1.5-V,1.6-V,1.8-V,2.5-V

Fixed-Output(ForAdjustableVersionsRefertoTPS72501)

InputVoltageDownto1.8V

Low170-mVDropoutVoltageat1A(TPS72625)

StableWithAnyType/ValueOutputCapacitorIntegratedSupervisor(SVS)With200-msRESETDelayTime

Low210-µAGroundCurrentatFullLoad(TPS72625)

Lessthan1-µAStandbyCurrent

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

ThermalandOvercurrentProtection

5-LeadSOT223-5orDDPAKSurface-MountPackage

DESCRIPTION

TheTPS726xxfamilyof1-Alow-dropout(LDO)linearregulatorshasfixedvoltageoptionsavailablethatarecommonlyusedtopowerthelatestDSPs,FPGAs,andmicrocontrollers.TheintegratedsupervisorycircuitryprovidesanactivelowRESETsignalwhentheoutputfallsoutofregulation.Thenocapaci-tor/anycapacitorfeatureallowsthecustomertotailoroutputtransientperformanceasneeded.Therefore,comparedtootherregulatorscapableofprovidingthesameoutputcurrent,thisfamilyofregulatorscanprovideastandalonepowersupplysolutionorapostregulatorforaswitchmodepowersupply.

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

Groundcurrentistypically210µAatfullloadanddropstolessthan80µAatnoload.Standbycurrentislessthan1µA.

EachregulatoroptionisavailableineitheraSOT223-5orDDPAKpackage.Withalowinputvoltageandproperlyheatsinkedpackage,theregu-latordissipatesmorepowerandachieveshigherefficienciesthansimilarregulatorsrequiring2.5Vormoreminimuminputvoltageandhigherquiescentcurrents.Thesefeaturesmakeitaviablepowersupplysolutionforportable,batterypoweredequip-ment.

Althoughanoutputcapacitorisnotrequiredforstability,transientresponseandoutputnoiseareimprovedwitha10-µFoutputcapacitor.

Unlikesomeregulatorsthathaveaminimumcurrentrequirement,theTPS726familyisstablewithnooutputloadcurrent.Thelownoisecapabilityofthisfamily,coupledwithitshighcurrentoperationandeaseofpowerdissipation,makeitidealfortelecomboards,modembanks,andothernoisesensitiveapplications.

••••••••••

APPLICATIONS

•••••

PCICardsModemBanksTelecomBoards

DSP,FPGA,andMicroprocessorPowerSupplies

Portable,Battery-PoweredApplications

DCQ PACKAGESOT223-5(TOP VIEW)ENABLEINGNDOUTRESET1234512345

KTT PACKAGE

DDPAK(TOP VIEW)

Note: Tab is GND for both packages

Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.

PRODUCTIONDATAinformationiscurrentasofpublicationdate.ProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.Productionprocessingdoesnotnecessarilyincludetestingofallparameters.

ENABLEINGNDOUTRESET Copyright©2002–2004,TexasInstrumentsIncorporated

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Thesedeviceshavelimitedbuilt-inESDprotection.TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.

ORDERINGINFORMATION

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

SOT223-5(3)TPS72615DCQTPS72616DCQTPS72618DCQTPS72625DCQSYMBOLPS72615PS72616PS72618PS72625DDPAK(4)TPS72615KTTTPS72616KTTTPS72618KTTTPS72625KTTSYMBOLTPS72615TPS72616TPS72618TPS72625Othervoltageoptionsareavailableuponrequestfromthemanufacturer.RefertoTPS72501foradjustableversion.

Toorderatapedandreeledpart,addthesuffixRtothepartnumber(e.g.,TPS72151DCQR).

Toordera50-piecereel,addthesuffixT(e.g.,TPS72615KTTT);toordera500-piecereel,addthesuffixR(e.g.,TPS72615KTTR).

overoperatingfree-airtemperaturerangeunlessotherwisenoted(1)

UNITInputvoltage,VI(2)VoltagerangeatEN,FBVoltageonOUT,RESETESDrating,HBMContinuoustotalpowerdissipationOperatingjunctiontemperaturerange,TJMAximumjunctiontemperaturerange,TJStoragetemperature,Tstg(1)(2)

-0.3to7-0.3toVI+0.362-50to150150-65to150VVVkV°C°C°CSeeDissipationRatingTableStressesbeyondthoselistedunderabsolutemaximumratingsmaycausepermanentdamagetothedevice.Thesearestressratingsonly,andfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderrecommendedoperatingconditionsisnotimplied.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.Allvoltagevaluesarewithrespecttonetworkgroundterminal.

MINNomMAXUNITInputvoltage,VI(1)Continuousoutputcurrent,IOOperatingjunctiontemperature,TJ(1)

MinimumVI=VO(nom)+VDO.

1.80-4061125VA°CPACKAGEDDPAKSOT223(1)(2)

BOARDHighK(1)LowK(2)RΘJC2°C/W15°C/WRΘJA23°C/W53°C/WTheJEDEChighK(2s2p)boarddesignusedtoderivethisdatawasa3-inchx3-inch(7,5-cmx7,5-cm),multilayerboardwith1ounceinternalpowerandgroundplanesand2ouncecoppertracesontopandbottomoftheboard.

TheJEDEClowK(1s)boarddesignusedtoderivethisdatawasa3-inchx3-inch(7,5-cmx7,5-cm),two-layerboardwith2ouncecoppertracesontopoftheboard.

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TPS72615,TPS72616TPS72618,TPS72625

SLVS403C–MAY2002–REVISEDMARCH2004

ELECTRICALCHARACTERISTICS

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

PARAMETERBandgapvoltagereferenceTPS72615TPS72616VOOutputvoltageTPS72618TPS72625IGroundcurrentStandbycurrentVnPSRROutputnoisevoltageRipplerejectionCurrentlimit(1)Outputvoltagelineregulation(∆VO/VO)(2)OutputvoltageloadregulationVIHVILIIENhighlevelinputENlowlevelinputENinputcurrentUVLOthresholdUVLOhysteresisUVLOdeglitchUVLOdelay(1)(2)

EN=0VorVIVCCrisingTJ=25°C,VCCrisingTJ=25°C,VCCrisingTJ=25°C,VCCrising1.45VO+1VLineregulation(mV)+(%ńV)

VO(5.5V*VImin)

1000

1003

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ELECTRICALCHARACTERISTICS(continued)

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

otherwisenoted)

PARAMETERTPS72625VDODropoutvoltageTPS72618MinimuminputvoltageforvalidRESETTripthresholdvoltageHysteresisvoltageRESETt(RESET)delaytimeRisingedgedeglitchOutputlowvoltage(at700µA)Leakagecurrent(3)

-0.3100(3)(3)TESTCONDITIONSIO=1AIO=1AIO=1AIO=1ATJ=25°CTJ=25°CMINTYP170MAX280UNIT2103201.3909310200100.410030096mVV%VOmVmsµsVnADropoutvoltageisdefinedasthedifferentialvoltagebetweenVOandVIwhenVOdrops100mVbelowthevaluemeasuredwithVI=VO+1V.

FUNCTIONALBLOCKDIAGRAM

TPS72615/16/18/25

INEN

1.220VrefGND

Current Limit/ ThermalProtectionOUT

DeglitchandDelay0.93󰀀× VrefRESETTerminalFunctions

TERMINALNAMEGNDENABLEINRESETNO.3125IIO/II/ODESCRIPTIONGroundEnableinputInputsupplyvoltageThisterminalistheRESEToutputterminal.Whenusedwithapullupresistor,thisopen-drainoutputprovidestheactivelowRESETsignalwhentheregulatoroutputvoltagedropsmorethan5%belowitsnominaloutputvoltage.TheRESETdelaytimeistypically200ms.RegulatedoutputvoltageOUT4O4

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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)VRESttRESETOutput200 msDelay200 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

TPS72618OUTPUTVOLTAGE

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 − µA200TPS72618OUTPUTVOLTAGE

vs

JUNCTIONTEMPERATURE

250TPS72618GROUNDCURRENT

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.

TPS72618GROUNDCURRENT

vs

OUTPUTCURRENT

200175Ground Current − µA15012510075502500.01

VDO− Dropout Voltage − mVFigure2.

TPS72625DCDROPOUTVOLTAGE

vs

OUTPUTCURRENT

300VO = 2.5 V (nom)VDO− Dropout Voltage − mV250200150100500TJ = −40°CTJ = 25°CTJ = 125°C250200150100500−40−25−105300Figure3.

TPS72618DROPOUTVOLTAGE

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.

MINIMUMREQUIREDINPUTVOLT-AGEvs

OUTPUTVOLTAGE

VI− Minimum Required Input Voltage − VVI− Input Voltage − V4.53.8Figure5.Figure6.

TPS72618LINETRANSIENT

RESPONSE

∆VO− Change inIO = 1 ACo = 10 µFOutput Voltage − mVTPS72618LOADTRANSIENT

RESPONSE

43.5TJ = 25°CTJ = 125°C1000−100VO = 2.8 VCo = 10 µFCi = 1 µF2.83VO− Output Voltage − mV2.5TJ = −40°C21.51.522.533.4.5VO − Output Voltage − V

1000−100050100150200250300350400450500t − Time − µs

IO− Output Current − A10.50051015202530304550t − Time − µs

Figure7.Figure8.Figure9.

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TYPICALCHARACTERISTICS(continued)

TPS72618OUTPUTVOLTAGE,

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 µF3210VOTPS72618LOADTRANSIENT

RESPONSE

∆VO− Change inIO − Output Current − AOutput Voltage − mVTPS72618POWERUP/POWER

DOWN

RL = 1.8 ΩCo = 1 µFCi = 1 µF1000VI = 2.8 VCo = 1 µFCI = 1 µF−100VI10.5005101520253030t − Time − µs

4550V − Output Voltage − VO01002003004005006007008009001000t − Time − µs

Figure10.

TPS72618OUTPUTSPECTRAL

NOISEDENSITY

vs

FREQUENCY

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

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

OUTPUTIMPEDANCE

vs

FREQUENCY

10IO = 1 A1IO = 1 mARipple Rejection − dB10090807060504030201001001 k10 k100 k1 MTPS72618RIPPLEREJECTION

vs

FREQUENCY

VI= 2.8 V,VO = 1.8 V,CO = 10 µFOutput Spectral Noise Density − µV/Zo− Output Impedance −Ω10 µF / 1mA0.10.01010VI = 2.8 VCo = 10 µFTJ = 25°󰀀C10 µF / 1A101001 k10 k100 k1 Mf − Frequency − Hz

f − Frequency − Hz

Figure13.CURRENTLIMIT

vs

INPUTVOLTAGE

200019001800Current Limit − A170016001500140013001200110010001.522.533.4.555.50012TJ = 25°CTJ = −40°CTJ = 125°CGround Current −µA600500400300200Figure14.

TPS72615GROUNDCURRENT

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

2.533.4.5VI − Input Voltage − V

55.5Figure16.Figure17.Figure18.

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APPLICATIONINFORMATION

TheTPS726xxfamilyoflow-dropout(LDO)regulatorshavenumerousfeaturesthatmakeitapplytoawide

rangeofapplications.Thefamilyoperateswithverylowinputvoltage(≥1.8V)andlowdropoutvoltage(typically200mVatfullload),makingitanefficientstand-alonepowersupplyorpostregulatorforbatteryorswitchmodepowersupplies.BoththeactivelowRESETand1-Aoutputcurrent,maketheTPS726xxfamilyidealforpoweringprocessorandFPGAsupplies.TheTPS726xxfamilyalsohaslowoutputnoise(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.

RegulatorProtection

TheTPS726xxpasselementhasabuilt-inbackdiodethatsafelyconductsreversecurrentwhentheinputvoltagedropsbelowtheoutputvoltage(e.g.,duringpowerdown).Currentisconductedfromtheoutputtotheinputandisnotinternallylimited.Ifextendedreversevoltageisanticipated,externallimitingmightbeappropriate.

TheTPS726xxalsofeaturesinternalcurrentlimitingandthermalprotection.Duringnormaloperation,theTPS726xxlimitsoutputcurrenttoapproximately1.6A.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

(1)

Where:

•VI(avg)istheaverageinputvoltage.•VO(avg)istheaverageoutputvoltage.•O(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.

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THERMALINFORMATION(continued)

Figure19illustratesthesethermalresistancesfor(a)aSOT223packagemountedinaJEDEClow-Kboard,and(b)aDDPAKpackagemountedonaJEDEChigh-Kboard.

A

CIRCUIT BOARD COPPER AREA

CBA

RθJC

BRθCS

CRθSA

DDPAK Package

(b)

CTCTJ

ABSOT223 Package

(a)

TA

Figure19.ThermalResistances

Equation2summarizesthecomputation:

TJ

+T)PDmaxxR)R)R

AθJCθCSθSA

ǒ

Ǔ

(2)

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,anddifferentairflows,etc.).Usingthesemodels,thethreethermalresistancescanbecombinedintoonethermalresistancebetweenjunctionandambient(RΘJA).ThisRΘJAisvalidonlyforthespecificoperatingenvironmentusedinthecomputermodel.

Equation2simplifiesintoEquation3:T+T)PDmaxxRJAθJARearrangingEquation3givesEquation4:

T–T

R+JAθJAPmax

D

(3)

(4)

UsingEquation3andthecomputermodelgeneratedcurvesshowninFigure20andFigure23,adesignercanquicklycomputetherequiredheatsinkthermalresistance/boardareaforagivenambienttemperature,powerdissipation,andoperatingenvironment.

DDPAKPowerDissipation

TheDDPAKpackageprovidesaneffectivemeansofmanagingpowerdissipationinsurfacemountapplications.TheDDPAKpackagedimensionsareprovidedintheMechanicalDatasectionattheendofthedatasheet.TheadditionofacopperplanedirectlyunderneaththeDDPAKpackageenhancesthethermalperformanceofthepackage.

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THERMALINFORMATION(continued)

Toillustrate,theTPS72625inaDDPAKpackagewaschosen.Forthisexample,theaverageinputvoltageis5

V,theoutputvoltageis2.5V,theaverageoutputcurrentis1A,theambienttemperature55°C,theairflowis150LFM,andtheoperatingenvironmentisthesameasdocumentedbelow.Neglectingthequiescentcurrent,themaximumaveragepoweris:

PDmax+(5*2.5)Vx1A+2.5W(5)SubstitutingTJmaxforTJintoEquation4givesEquation6:Rmax+(125*55)°Cń2.5W+28°CńWθJA

(6)

FromFigure20,DDPAKThermalResistancevsCopperHeatsinkArea,thegroundplaneneedstobe1cm2fortheparttodissipate2.5W.TheoperatingenvironmentusedinthecomputermodeltoconstructFigure20consistedofastandardJEDECHigh-Kboard(2S2P)witha1oz.internalcopperplaneandgroundplane.Thepackageissolderedtoa2oz.copperpad.Thepadistiedthroughthermalviastothe1oz.groundplane.Figure21showsthesideviewoftheoperatingenvironmentusedinthecomputermodel.

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

100Figure20.DDPAKThermalResistancevsCopperHeatsinkArea

2 oz. Copper Solder Padwith 25 Thermal Vias1 oz. CopperPower Plane1 oz. CopperGround PlaneThermal Vias, 0,3 mmDiameter, 1,5 mm Pitch

Figure21.DDPAKThermalResistance

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THERMALINFORMATION(continued)

FromthedatainFigure22andrearrangingEquation4,themaximumpowerdissipationforadifferentgroundplaneareaandaspecificambienttemperaturecanbecomputed.

TA = 55°CPD− Maximum Power Dissipation − WTJM− Maximum Junction Temperature − 125°C100250 LFM150 LFM3No Air Flow210.1110Copper Heatsink Area − cm2

Figure22.MaximumPowerDissipationvsCopperHeatsinkArea

SOT223PowerDissipation

TheSOT223packageprovidesaneffectivemeansofmanagingpowerdissipationinsurfacemountapplications.TheSOT223packagedimensionsareprovidedintheMechanicalDatasectionattheendofthedatasheet.TheadditionofacopperplanedirectlyunderneaththeSOT223packageenhancesthethermalperformanceofthepackage.

Toillustrate,theTPS72625inaSOT223packagewaschosen.Forthisexample,theaverageinputvoltageis3.3V,theoutputvoltageis2.5V,theaverageoutputcurrentis1A,theambienttemperature55°C,noairflowispresent,andtheoperatingenvironmentisthesameasdocumentedbelow.Neglectingthequiescentcurrent,themaximumaveragepoweris:

PDmax+(3.3*2.5)Vx1A+800mW(7)SubstitutingTJmaxforTJintoEquation4givesEquation8:Rmax+(125*55)°Cń800mW+87.5°CńWθJA

(8)

FromFigure23,RΘJAvsPCBCopperArea,thegroundplaneneedstobe0.55in2fortheparttodissipate800mW.TheoperatingenvironmentusedtoconstructFigure23consistedofaboardwith1oz.copperplanes.Thepackageissolderedtoa1oz.copperpadonthetopoftheboard.Thepadistiedthroughthermalviastothe1oz.groundplane.

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THERMALINFORMATION(continued)

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

10No Air FlowFigure23.SOT223ThermalResistancevsPCBAREA

FromthedatainFigure23andrearrangingEquation4,themaximumpowerdissipationforadifferentgroundplaneareaandaspecificambienttemperaturecanbecomputed(asshowninFigure24).6TA = 25°CPD− Maximum Power Dissipation − W4 in2 PCB Area30.5 in2 PCB Area2100255075100125150TA − Ambient Temperature − °C

Figure24.SOT223PowerDissipation

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Copyright  2004, Texas Instruments Incorporated

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