TPS79433DGNT资料

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TPS79401,TPS79418TPS79425,TPS79428TPS79430,TPS79433

SLVS349D–NOVEMBER2001–REVISEDOCTOBER2004

ULTRALOW-NOISE,HIGHPSRR,FASTRF250-mALOW-DROPOUTLINEAR

REGULATORS

FEATURES

•••••••••

250-mALow-DropoutRegulatorWithEnableAvailablein1.8V,2.5V,2.8V,3V,3.3V,andAdjustable(1.2Vto5.5V)HighPSRR(60dBat10kHz)

UltralowNoise(32µVrms,TPS79428)FastStart-UpTime(50µs)

StableWitha2.2-µFCeramicCapacitorExcellentLoad/LineTransientResponseVeryLowDropoutVoltage(155mVatFullLoad)

AvailableinMSOP-8andSOT223-6Packages

DESCRIPTION

TheTPS794xxfamilyoflow-dropout(LDO)linearvoltageregulatorsfeatureshighpower-supplyrejec-tionratio(PSRR),ultralow-noise,faststart-up,andexcellentlineandloadtransientresponsesinsmalloutline,MSOP-8PowerPAD™andSOT223-6pack-ages.Eachdeviceinthefamilyisstablewithasmall2.2-µFceramiccapacitorontheoutput.Thefamilyusesanadvanced,proprietaryBiCMOSfabricationprocesstoyieldextremelylowdropoutvoltages(e.g.,155mVat250mA).Eachdeviceachievesfaststart-uptimes(approximately50µswitha0.001-µFbypasscapacitor)whileconsuminglowquiescentcurrent(170µAtypical).Moreover,whenthedeviceisplacedinstandbymode,thesupplycurrentisreducedtolessthan1µA.TheTPS79428exhibitsapproximately32µVRMSofoutputvoltagenoiseat2.8Voutputwitha0.1-µFbypasscapacitor.Appli-cationswithanalogcomponentsthatarenoise-sensitive,suchasportableRFelectronics,benefitfromthehighPSRRandlownoisefeaturesaswellasthefastresponsetime.

TPS79428

APPLICATIONS

•••••

RF:VCOs,Receivers,ADCsAudio

Bluetooth™,WirelessLAN

CellularandCordlessTelephonesHandheldOrganizers,PDAs

DGN PACKAGEMSOP PowerPAD(TOP VIEW)OUTNCFBNR

12348765TPS79433

80Ripple Rejection (dB)70605040302010010IOUT = 10 mAIOUT = 250 mAOutput Spectral Noise Density (µV/√Hz)INNCENGND

RIPPLE REJECTION

vs

FREQUENCY90OUTPUT SPECTRAL NOISE DENSITY

vs

FREQUENCY0.350.300.250.200.150.100.050

IOUT = 1 mAIOUT = 250 mACOUT = 2.2 µF,CNR = 0.1 µF,VIN = 3.8 VNC − No internal connectionDCQ PACKAGESOT223-6(TOP VIEW)

ENINGNDOUTNR

12345

6GND

VIN = 4.3 V,VOUT = 3.3 V,CIN = 1 µF,COUT = 10 µF,CNR = 0.01 µF1001 k10 k100 k1 M10 M100100010000100000Frequency (Hz)Frequency (Hz)

Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.

BluetoothisatrademarkofBluetoothSIG,Inc.PowerPADisatrademarkofTexasInstruments.

Allothertrademarksarethepropertyoftheirrespectiveowners.

PRODUCTIONDATAinformationiscurrentasofpublicationdate.ProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.Productionprocessingdoesnotnecessarilyincludetestingofallparameters.

Copyright©2001–2004,TexasInstrumentsIncorporated

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ThisintegratedcircuitcanbedamagedbyESD.TexasInstrumentsrecommendsthatallintegratedcircuitsbehandledwithappropriateprecautions.Failuretoobserveproperhandlingandinstallationprocedurescancausedamage.

ESDdamagecanrangefromsubtleperformancedegradationtocompletedevicefailure.Precisionintegratedcircuitsmaybemoresusceptibletodamagebecauseverysmallparametricchangescouldcausethedevicenottomeetitspublishedspecifications.

ORDERINGINFORMATION

PRODUCT

VOLTAGE

PACKAGEMSOP-8

TPS79401

Adjustable

SOT223-6MSOP-8

TPS79418

1.8V

SOT223-6MSOP-8

TPS79423

2.5V

SOT223-6

-40°Cto125°C

MSOP-8

TPS79428

2.8V

SOT223-6MSOP-8

TPS79430

3V

SOT223-6MSOP-8

TPS79433

3.3V

SOT223-6

PS79433PS79430AYEPS79428AYDAYCPS79425PS79418AYBPS79401AXM

TJ

SYMBOLAXL

PARTNUMBERTPS79401DGNRTPS79401DGNTTPS79401DCQRTPS79401DCQTPS79418DGNRTPS79418DGNTTPS79418DCQRTPS79418DCQTPS79425DGNRTPS79425DGNTTPS79425DCQRTPS79425DCQTPS79428DGNRTPS79428DGNTTPS79428DCQRTPS79428DCQTPS79430DGNRTPS79430DGNTTPS79430DCQRTPS79430DCQTPS79433DGNRTPS79433DGNTTPS79433DCQRTPS79433DCQ

TRANSPORTMEDIA,

QUANTITYTapeandReel,2500TapeandReel,250TapeandReel,2500

Tube,78TapeandReel,2500TapeandReel,250TapeandReel,2500

Tube,78TapeandReel,2500TapeandReel,250TapeandReel,2500

Tube,78TapeandReel,2500TapeandReel,250TapeandReel,2500

Tube,78TapeandReel,2500TapeandReel,250TapeandReel,2500

Tube,78TapeandReel,2500TapeandReel,250TapeandReel,2500

Tube,78

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SLVS349D–NOVEMBER2001–REVISEDOCTOBER2004

ABSOLUTEMAXIMUMRATINGS

overoperatingtemperaturerangeunlessotherwisenoted(1)

VALUE

VINrangeVENrangeVOUTrangePeakoutputcurrentESDrating,HBMESDrating,CDM

ContinuoustotalpowerdissipationJunctiontemperaturerange,TJStoragetemperaturerange,Tstg(1)

-0.3Vto6V-0.3VtoVIN+0.3V

-0.3Vto6VInternallylimited

2kV500V

SeeDissipationRatingsTable

-40°Cto150°C-65°Cto150°C

Stressesbeyondthoselistedunderabsolutemaximumratingsmaycausepermanentdamagetothedevice.Thesearestressratingsonly,andfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderrecommendedoperatingconditionsisnotimplied.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.

PACKAGEDISSIPATIONRATINGS

PACKAGE

AIRFLOW(CFM)

0

DGN

150250

654PD (W)Condition 13Condition 22100255075100TA (°C)

125150RθJC(°C/W)

8.478.218.20

RθJA(°C/W)55.0949.9748.10

TA≤25°CPOWERRATING

2.27W2.50W2.60W

TA=70°CPOWERRATING

1.45W1.60W1.66W

TA=85°CPOWERRATING

1.18W1.30W1.35W

CONDITIONS

12

PACKAGESOT223SOT223

PCB AREA4in2 Top Side Only0.5in2 Top Side Only

θJA53°C/W110°C/W

Figure1.SOT223PowerDissipation

3

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ELECTRICALCHARACTERISTICS

Overrecommendedoperatingtemperaturerange(TJ=-40°Cto125°C),VEN=VIN,VIN=VOUT(nom)+1V(1),IOUT=1mA,COUT=10µF,CNR=0.01µF,unlessotherwisenoted.Typicalvaluesareat25°C.

PARAMETER

VINIOUTVFB

Inputvoltage(1)

ContinuousoutputcurrentInternalreferenceAccuracy(1)

Outputvoltagelineregulation(∆VOUT%/∆VIN)(1)

Loadregulation(∆VOUT%/∆IOUT)Dropoutvoltage(2)

VIN=VOUT(nom)-0.1VOutputcurrentlimitGroundpincurrentShutdowncurrent(3)FBpincurrentPower-supplyripplerejection

TPS79428TPS79428TPS79430TPS79433TPS79401TPS79401

VOUT+1V≤VIN≤5.5VVOUT+1V0µAIOUT=250mAIOUT=250mAIOUT=250mACNR=0.001µF

Outputnoisevoltage(TPS79428)

CNR=0.0047µFCNR=0.01µFCNR=0.1µFCNR=0.001µF

Time,start-up(TPS79428)High-levelenableinputvoltageLow-levelenableinputvoltageENpincurrentUVLOthresholdUVLOhysteresis

(1)(2)(3)

MinimumVINis2.7VorVOUT+VDO,whicheverisgreater.

DropoutisnotmeasuredfortheTPS79418andTPS79425sinceminimumVIN=2.7V.

Foradjustableversions,thisappliesonlyafterVINisapplied;thenVENtransitionshightolow.

RL-14Ω,COUT=1µF2.7VCNR=0.0047µFCNR=0.01µF

1.7012.25

100656040553633325070100

VIN0.712.65

VVµAVmVµsµVRMSdB

2.7VTJ=25°C

TESTCONDITIONS

MIN2.701.220VFB-3.0

0.05101551551459251700.07

22011210210200

mAµAµAµAmV

1.225TYP

MAX5.52501.2305.5-VDO

+3.00.12

UNITVmAVV%%/VmV

VOUTOutputvoltagerange

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SLVS349D–NOVEMBER2001–REVISEDOCTOBER2004

FUNCTIONALBLOCKDIAGRAM—ADJUSTABLEVERSION

IN

UVLOCurrentSenseILIMGNDEN

ThermalShutdownBandgapReference1.225 VUVLOR2Quickstart250 kΩVrefExternal tothe DeviceNR(1)_SHUTDOWN+FBR1OUTVIN(1) Not Available on DCQ (SOT223) options.FUNCTIONALBLOCKDIAGRAM—FIXEDVERSION

IN

UVLOGNDEN

ThermalShutdownQuickstartBandgapReference1.225 V250 kΩVrefCurrentSenseILIM_UVLOR2R2 = 40kNR

SHUTDOWN+R1OUT

VINTerminalFunctions

TERMINAL

NAMENRENFBGNDINNCOUT

DGN(MSOP)

4635,PAD82,71

4DCQ(SOT223)

51532

DESCRIPTION

Connectinganexternalcapacitortothispinbypassesnoisegeneratedbytheinternalbandgap.Thisimprovespower-supplyrejectionandreducesoutputnoise.

TheENterminalisaninputwhichenablesorshutsdownthedevice.WhenENgoestoalogichigh,thedevicewillbeenabled.Whenthedevicegoestoalogiclow,thedeviceisinshutdownmode.Thisterminalisthefeedbackinputvoltagefortheadjustabledevice.Regulatorground.

Unregulatedinputtothedevice.Nointernalconnection.Outputoftheregulator.

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TYPICALCHARACTERISTICS

TPS79433OUTPUTVOLTAGE

vs

OUTPUTCURRENT

3.2903.2853.280

2.790VOUT(V)VOUT(V)2.7852.7802.7752.7702.7650

50

100IOUT (mA)

200

250

IOUT = 200 mAIGND (µA)3.2753.2703.2653.2603.2553.250

VIN = 3.8 VCOUT = 10 µF175170165160155150−40−25−105IOUT = 250 mA2.8002.795IOUT = 1 mATPS79428OUTPUTVOLTAGE

vs

JUNCTIONTEMPERATURE

190185180TPS79428GROUNDCURRENT

vs

JUNCTIONTEMPERATURE

VIN = 3.8 V,COUT = 10 µFIOUT = 1 mA−40−25−105203550658095110125TJ (°C)203550658095110125TJ (°C)

Figure2.

TPS79428OUTPUTSPECTRAL

NOISEDENSITY

vs

FREQUENCY

0.35Output Spectral Noise Density (µV/√Hz)0.300.250.20

IOUT = 250 mA0.150.100.050100100010000100000Frequency (Hz)

IOUT = 1 mA0.35Output Spectral Noise Density (µV/√Hz)Figure3.

TPS79428OUTPUTSPECTRAL

NOISEDENSITY

vs

FREQUENCY

1.8Output Spectral Noise Density (µV/√Hz)COUT = 10 µF,CNR = 0.1 µF,VIN = 3.8 V1.61.41.21.00.80.60.40.20100Figure4.

TPS79428OUTPUTSPECTRAL

NOISEDENSITY

vs

FREQUENCY

COUT = 10 µF,IOUT = 250 mAVIN = 3.8 VCNR = 0.001 µFCNR = 0.0047 µFCNR = 0.01 µFCNR = 0.1 µFCOUT = 2.2 µF,CNR = 0.1 µF,VIN = 3.8 V0.300.250.200.150.100.050100IOUT = 1 mAIOUT = 250 mA100010000100000100010000100000Frequency (Hz)

Frequency (Hz)

Figure5.

TPS79428ROOTMEANSQUARED

OUTPUTNOISE

vsCNR

605040IOUT = 250 mA,COUT = 10 µF ZO, Output Impedance (Ω)10Figure6.Figure7.

TPS79433OUTPUTIMPEDANCE

vs

FREQUENCY

250VIN = 4.3 V,COUT = 10 µF,2001IOUT = 1 mAVDO (mV)150TPS79428DROPOUTVOLTAGE

vs

JUNCTIONTEMPERATURE

VIN = 3.8 V,COUT = 10 µFIOUT = 250 mARMS Output Noise (µVRMS)30201000.001

1000.100IOUT = 250 mA50IOUT = 1 mA203550658095110125TJ (°C)

0.0200.00470.01

CNR (µF)

0.1

101001 k10 k100 k1 M10 MFrequency (Hz)

0−40−25−105Figure8.Figure9.Figure10.

6

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SLVS349D–NOVEMBER2001–REVISEDOCTOBER2004

TYPICALCHARACTERISTICS(continued)

TPS79433RIPPLEREJECTION

vs

FREQUENCY

908070Ripple Rejection (dB)605040302010010VIN = 4.3 V,VOUT = 3.3 V,CIN = 1 µF,COUT = 10 µF,CNR = 0.01 µF1001 k10 k100 k1 M10 MIOUT = 10 mARipple Rejection (dB)IOUT = 250 mA908070605040302010010VIN = 4.3 V,VOUT = 3.3 V,CIN = 1 µF,COUT = 2.2 µF,CNR = 0.01 µF1001 k10 k100 k1 M10 MIOUT = 10 mARipple Rejection (dB)IOUT = 250 mATPS79433RIPPLEREJECTION

vs

FREQUENCY

908070605040302010010TPS79433RIPPLEREJECTION

vs

FREQUENCY

IOUT = 10 mAIOUT = 250 mAVIN = 4.3 V,VOUT = 3.3 V,CIN = 1 µF,COUT = 2.2 µF,CNR = 0.1 µF1001 k10 k100 k1 M10 MFrequency (Hz)Frequency (Hz)Frequency (Hz)

Figure11.

TPS79433OUTPUTVOLTAGE,

ENABLEVOLTAGE

vs

TIME(START-UP)

6.0V_EnableFigure12.Figure13.

TPS79433

LINETRANSIENTRESPONSE

VIN (V)IOUT (mA)5.55.04.510∆VOUT (mV)∆VOUT (mV)IOUT = 250 mA,COUT = 10 µF,CNR = 0.1 µF, dv/dt = 1 V/µs250TPS79433

LOADTRANSIENTRESPONSE

42VOUT, VEN (V)0VIN = 4.3 V,VOUT = 3.3 V,IOUT = 250 mA,COUT = 2.2 µF032100801602403204004805600720800Time (µs)

CNR = 0.0047 µFCNR = 0.001 µF0−10−20−300100200300400500500−50VIN = 4.3 V,COUT = 10 µF0306090Time (µs)

didt120+1500.02Ams180210Time (µs)

Figure14.Figure15.

TPS79433DROPOUTVOLTAGE

vs

OUTPUTCURRENT

200250TA = 125°CFigure16.

TPS79401DROPOUTVOLTAGE

vs

INPUTVOLTAGE

TA = 125°C200TA = 25°CTPS79425

POWER-UP/POWER-DOWN

4.54.0Power-Up (500 mV/div)3.53.02.52.01.51.00.50−0.501.42.84.25.67.08.49.8t (ms)

0VOUTVOUT = 2.5 V,RL = 10 ΩVINVDO (mV)150TA = 25°CVDO (mV)150100TA = −40°C50100TA = −40°C500255075100125150175200225250IOUT (mA)

02.5COUT = 10 µF,CNR = 0.01 µF,IOUT = 250 mA3.03.5VIN (V)

4.04.55.0Figure17.Figure18.Figure19.

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TYPICALCHARACTERISTICS(continued)

TPS79428TYPICALREGIONSOFSTABILITYEQUIVALENTSERIES

RESISTANCE(ESR)

vs

OUTPUTCURRENT

100ESR, Equivalent Series Resistance (Ω)ESR, Equivalent Series Resistance (Ω)COUT = 2.2 µFTA = −40 to 85°C10Region of InstabilityTPS79428TYPICALREGIONSOFSTABILITYEQUIVALENTSERIES

RESISTANCE(ESR)

vs

OUTPUTCURRENT

100COUT = 10 µFTA = −40 to 85°C10Region of Instability110.1Region of Stability0.010255075100125150175200225250IOUT (mA)

0.1Region of Stability0.0111020406080IOUT (mA)

120200250Figure20.Figure21.

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APPLICATIONINFORMATION

TheTPS794xxfamilyoflow-dropout(LDO)regulatorshasbeenoptimizedforuseinnoise-sensitiveequipment.Thedevicefeaturesextremelylowdropoutvoltages,highPSRR,ultralowoutputnoise,lowquiescentcurrent,andenableinputtoreducesupplycurrentstolessthan1µAwhentheregulatoristurnedoff.AtypicalapplicationcircuitisshowninFigure22.VININTPS794xxEN0.1µF0.01µFGNDNR2.2µFOUTVOUT

Figure22.TypicalApplicationCircuit

ExternalCapacitorRequirements

A0.1-µForlargerceramicinputbypasscapacitor,connectedbetweenINandGNDandlocatedclosetotheTPS794xx,isrequiredforstability.Itimprovestransientresponse,noiserejection,andripplerejection.Ahigher-valueinputcapacitormaybenecessaryiflarge,fast-rise-timeloadtransientsareanticipatedorthedeviceislocatedseveralinchesfromthepowersource.

Likemostlowdropoutregulators,theTPS794xxrequiresanoutputcapacitorconnectedbetweenOUTandGNDtostabilizetheinternalcontrolloop.Theminimumrecommendedcapacitanceis2.2µF.Any2.2µForlargerceramiccapacitorissuitable.

TheinternalvoltagereferenceisakeysourceofnoiseinanLDOregulator.TheTPS794xxhasanNRpinwhichisconnectedtothevoltagereferencethrougha250-kΩinternalresistor.The250-kΩinternalresistor,inconjunctionwithanexternalbypasscapacitorconnectedtotheNRpin,createsalow-passfiltertoreducethevoltagereferencenoiseand,therefore,thenoiseattheregulatoroutput.Inorderfortheregulatortooperateproperly,thecurrentflowoutoftheNRpinmustbeataminimum,becauseanyleakagecurrentcreatesanIRdropacrosstheinternalresistorthuscreatinganoutputerror.Therefore,theNRcapacitormusthaveminimalleakagecurrent.Thebypasscapacitorshouldbenomorethan0.1µFtoensurethatitisfullychargedduringthequickstarttimeprovidedbytheinternalswitchshowninthefunctionalblockdiagram.

Forexample,theTPS79428exhibitsonly32µVRMSofoutputvoltagenoiseusinga0.1-µFceramicNRcapacitoranda2.2-µFceramicoutputcapacitor.NotethattheoutputstartsupslowerasthebypasscapacitanceincreasesduetotheRCtimeconstantattheNRpinthatiscreatedbytheinternal250-kΩresistorandexternalcapacitor.

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BoardLayoutRecommendationtoImprovePSRRandNoisePerformance

ToimproveacmeasurementslikePSRR,outputnoise,andtransientresponse,itisrecommendedthattheboardbedesignedwithseparategroundplanesforVINandVOUT,witheachgroundplaneconnectedonlyatthegroundpinofthedevice.Inaddition,thegroundconnectionforthebypasscapacitorshouldconnectdirectlytothegroundpinofthedevice.

THERMAL RESISTANCE

vs

PCB COPPER AREA180Thermal Resistance −θJA(°C/W)160140120100806040200SOT223 Surface-Mount Package

012345PCB Copper Area − in

Surface-Mount Package1 oz. CopperCIRCUIT BOARD COPPER AREAFigure23.ThermalResistancevsPCBAreafortheSOT223-6.

PowerandDissipationandJunctionTemperature

Specifiedregulatoroperationisassuredtoajunctiontemperatureof125°C;themaximumjunctiontemperatureshouldberestrictedto125°Cundernormaloperatingconditions.Thisrestrictionlimitsthepowerdissipationtheregulatorcanhandleinanygivenapplication.Toensurethejunctiontemperatureiswithinacceptablelimits,calculatethemaximumallowabledissipation,PD(max),andtheactualdissipation,PD,whichmustbelessthanorequaltoPD(max).

Themaximum-power-dissipationlimitisdeterminedusingthefollowingequation:

Tmax*T

AP+J

D(max)R

θJA

(1)

where:

•TJmaxisthemaximumallowablejunctiontemperature.

•RθJAisthethermalresistencejuntion-to-ambientforthepackage.Seethepowerdissipationtableand

Figure1•TAistheambienttemperature.

Theregulatordissipationiscalculatedusing:

PD+V

ǒ

IN

*V

OUT

Ǔ IOUT

(2)

Powerdissipationresultingfromquiescentcurrentisnegligible.Excessivepowerdissipationtriggersthethermalprotectioncircuit.

RegulatorMounting

ThetaboftheSOT223-6packageiselectricallyconnectedtoground.Forbestthermalperformance,thetabofthesurface-mountversionshouldbesoldereddirectlytoacircuit-boardcopperarea.Increasingthecopperareaimprovesheatdissipation.SolderpadfootprintrecommendationsforthedevicesarepresentedinanapplicationbulletinSolderPadRecommendationsforSurface-MountDevices,literaturenumberAB-132,availablefromtheTIwebsite(www.ti.com).

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ProgrammingtheTPS79401AdjustableLDORegulator

TheoutputvoltageoftheTPS79401adjustableregulatorisprogrammedusinganexternalresistordividerasshowninFigure24.Theoutputvoltageiscalculatedusing:

VOUT

+V

REF

1)R1R2

ǒǓ(3)

where:

•VREF=1.2246Vtyp(theinternalreferencevoltage).

ResistorsR1andR2shouldbechosenforapproximately40-µAdividercurrent.Lowervalueresistorscanbeusedforimprovednoiseperformance,butthedevicewastesmorepower.HighervaluesshouldbeavoidedasleakagecurrentatFBincreasestheoutputvoltageerror.TherecommendeddesignprocedureistochooseR2=30.1kΩtosetthedividercurrentat40µA,C1=15pFforstability,andthencalculateR1using:

R1+

ǒV

OUT*1V

REF

Ǔ

R2

(4)

Inordertoimprovethestabilityoftheadjustableversion,itissuggestedthatasmallcompensationcapacitorbeplacedbetweenOUTandFB.Forvoltages<1.8V,thevalueofthiscapacitorshouldbe100pF.Forvoltages>1.8V,theapproximatevalueofthiscapacitorcanbecalculatedas:

(3x10–7)x(R1)R2)

C1+

(R1xR2)(5)Thesuggestedvalueofthiscapacitorforseveralresistorratiosisshowninthetablebelow.Ifthiscapacitoris

notused(suchasinaunity-gainconfiguration)orifanoutputvoltage<1.8Vischosen,thentheminimumrecommendedoutputcapacitoris4.7µFinsteadof2.2µF.

OUTPUT VOLTAGEPROGRAMMING GUIDE

VIN1µFINENNR0.01µFTPS794xxGNDFBR2OUTR1C1VOUT2.2µF

OUTPUTVOLTAGE

2.5 V3.3 V3.6 V

R1R2C122 pF15 pF15 pF

31.6 kΩ30.1 kΩ49.9 kΩ30.1 kΩ59 kΩ30.1 kΩ

†

Not Available on the DCQ package.

Figure24.TPS79401AdjustableLDORegulatorProgramming

RegulatorProtection

TheTPS794xxPMOS-passtransistorhasabuilt-inbackdiodethatconductsreversecurrentwhentheinputvoltagedropsbelowtheoutputvoltage(e.g.,duringpower-down).Currentisconductedfromtheoutputtotheinputandisnotinternallylimited.Ifextendedreversevoltageoperationisanticipated,externallimitingmightbeappropriate.

TheTPS794xxfeaturesinternalcurrentlimitingandthermalprotection.Duringnormaloperation,theTPS794xxlimitsoutputcurrenttoapproximately925mA.Whencurrentlimitingengages,theoutputvoltagescalesbacklinearlyuntiltheovercurrentconditionends.Whilecurrentlimitingisdesignedtopreventgrossdevicefailure,careshouldbetakennottoexceedthepowerdissipationratingsofthepackageortheabsolutemaximumvoltageratingofthedevice.Ifthetemperatureofthedeviceexceedsapproximately165°C,thermal-protectioncircuitryshutsitdown.Oncethedevicehascooleddowntobelowapproximately140°C,regulatoroperationresumes.

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