LP38692_电源芯片

LP38690-ADJ/LP38692-ADJ

1ALowDropoutCMOSLinearRegulatorswithAdjustableOutput

StablewithCeramicOutputCapacitors

GeneralDescription

TheLP38690/2-ADJlowdropoutCMOSlinearregulatorsprovide2.5%precisionreferencevoltage,extremelylowdropoutvoltage(450mV@1Aloadcurrent,VOUT=5V)andexcellentACperformanceutilizingultralowESRceramicoutputcapacitors.

ThelowthermalresistanceoftheLLPandSOT-223pack-agesallowthefulloperatingcurrenttobeusedeveninhighambienttemperatureenvironments.

TheuseofaPMOSpowertransistormeansthatnoDCbasedrivecurrentisrequiredtobiasitallowinggroundpincurrenttoremainbelow100µAregardlessofloadcurrent,inputvoltage,oroperatingtemperature.

DropoutVoltage:450mV(typ)@1A(typ.5Vout).GroundPinCurrent:55µA(typ)atfullload.AdjustPinVoltage:2.5%(25˚C)accuracy.

Features

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Outputvoltagerangeof1.25V-9V

2.5%adjustpinvoltageaccuracy(25˚C)

Lowdropoutvoltage:450mV@1A(typ,5Vout)Wideinputvoltagerange(2.7Vto10V)Precision(trimmed)bandgapreferenceGuaranteedspecsfor-40˚Cto+125˚C1µAoff-statequiescentcurrentThermaloverloadprotectionFoldbackcurrentlimiting

SOT-223and6-LeadLLPpackagesEnablepin(LP38692-ADJ)

Applications

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HardDiskDrivesNotebookComputersBatteryPoweredDevicesPortableInstrumentation

TypicalApplicationCircuits

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VOUT=VADJx(1+R1/R2)

Note:*Minimumvaluerequiredforstability.

©2005NationalSemiconductorCorporationDS201267www.national.com

LP38690-ADJ/LP38692-ADJConnectionDiagrams

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SOT-223,TopViewLP38692MP-ADJ

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6-LeadLLP,BottomView

LP38690SD-ADJ6-LeadLLP,BottomView

LP38692SD-ADJ

PinDescription

PINVINGNDVOUTVENADJ

DESCRIPTION

Thisistheinputsupplyvoltagetotheregulator.ForLLPpackagedevices,bothVINpinsmustbetiedtogetherforfullcurrentoperation(500mAmaximumperpin).

Circuitgroundfortheregulator.Thisisconnectedtothediethroughtheleadframe,andalsofunctionsastheheatsinkwhenthelargegroundpadissoldereddowntoacopperplane.Regulatedoutputvoltage.

TheenablepinallowstheparttobeturnedONandOFFbypullingthispinhighorlow.

TheadjustpinisusedtosettheregulatedoutputvoltagebyconnectingittotheexternalresistorsR1andR2(seeTypicalApplicationCircuit).

OrderingInformation

OrderNumberLP38690SD-ADJLP38692SD-ADJLP38692MP-ADJLP38690SDX-ADJLP38692SDX-ADJLP38692MPX-ADJ

PackageMarking

L112BL122BLJNBL112BL122BLJNB

PackageType6-LeadLLP6-LeadLLPSOT-2236-LeadLLP6-LeadLLPSOT-223

PackageDrawing

SDE06ASDE06AMP05ASDE06ASDE06AMP05A

SuppliedAs1000UnitsTapeandReel1000UnitsTapeandReel1000UnitsTapeandReel4500UnitsTapeandReel4500UnitsTapeandReel2000UnitsTapeandReel

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LP38690-ADJ/LP38692-ADJAbsoluteMaximumRatings(Note1)

IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.StorageTemperatureRangeLeadTemp.(Soldering,5seconds)ESDRating(Note3)PowerDissipation(Note2)

V(max)Allpins(withrespecttoGND)

−65˚Cto+150˚C

260˚C2kV

InternallyLimited

-0.3Vto12V

IOUTJunctionTemperature

InternallyLimited−40˚Cto+150˚C

OperatingRatings

VINSupplyVoltageOperatingJunctionTemperatureRange

2.7Vto10V−40˚Cto+125˚C

LimitsinstandardtypefaceareforTJ=25˚C,andlimitsinboldfacetypeapply

overthefulloperatingtemperaturerange.Unlessotherwisespecified:VIN=VOUT+1V,CIN=COUT=10µF,ILOAD=10mA.Min/Maxlimitsareguaranteedthroughtesting,statisticalcorrelation,ordesign.Symbol

Parameter

VIN=2.7V

VADJ∆VO/∆VIN∆VO/∆ILADJPinVoltage

OutputVoltageLineRegulation(Note6)

OutputVoltageLoadRegulation(Note7)

3.2V≤VIN≤10V100µAVIN-VODropoutVoltage(Note8)

(VO=3.3V)IL=0.1AIL=1A(VO=5V)IL=0.1AIL=1A

IQIL(MIN)IFBPSRRTSDTSD(HYST)IADJQuiescentCurrentMinimumLoadCurrentFoldbackCurrentLimitRippleRejection

ThermalShutdownActivation(JunctionTemp)

ThermalShutdownHysteresis(JunctionTemp)

ADJInputLeakageCurrent

VADJ=0-1.5VVIN=10V

-100

VIN≤10V,IL=100µA-1AVEN≤0.4V,(LP38692-ADJOnly)VIN-VO≤4VVIN-VO>5VVIN-VO<4V

VIN=VO+2V(DC),with1V(p-p)/120HzRipple

450150055160

˚C

100.01

100

nA

Conditions

Min1.2191.187

Typ(Note4)1.251.250.031.508080065650450550.001

Max1.2811.3130.151600145130011010001008001001100

mAdBµAmVVUnits

ElectricalCharacteristics

%/V%/A

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LP38690-ADJ/LP38692-ADJElectricalCharacteristicsLimitsinstandardtypefaceareforTJ=25˚C,andlimitsinboldfacetypeapply

overthefulloperatingtemperaturerange.Unlessotherwisespecified:VIN=VOUT+1V,CIN=COUT=10µF,ILOAD=10mA.Min/Maxlimitsareguaranteedthroughtesting,statisticalcorrelation,ordesign.(Continued)SymbolenVO(LEAK)VENParameter

OutputNoise

OutputLeakageCurrentEnableVoltage(LP38692-ADJOnly)

Conditions

BW=10Hzto10kHzVO=3.3V

VO=VO(NOM)+1V@10VINOutput=OFF

Output=ON,VIN=4VOutput=ON,VIN=6VOutput=ON,VIN=10V

IENEnablePinLeakage(LP38692-ADJOnly)

VEN=0Vor10V,VIN=10V

1.83.04.0-1

0.001

1

µA

Min

Typ(Note4)0.70.5

20.4

V

Max

UnitsµV/µA

Note1:Absolutemaximumratingsindicatelimitsbeyondwhichdamagetothecomponentmayoccur.Operatingratingsindicateconditionsforwhichthedeviceisintendedtobefunctional,butdonotguaranteespecificperformancelimits.Forguaranteedspecifications,seeElectricalCharacteristics.Specificationsdonotapplywhenoperatingthedeviceoutsideofitsratedoperatingconditions.

Note2:Atelevatedtemperatures,devicepowerdissipationmustbederatedbasedonpackagethermalresistanceandheatsinkvalues(ifaheatsinkisused).Thejunction-to-ambientthermalresistance(θJ-A)fortheSOT-223isapproximately125˚C/WforaPCboardmountingwiththedevicesoldereddowntominimumcopperarea(lessthan0.1squareinch).IfonesquareinchofcopperisusedasaheatdissipatorfortheSOT-223,theθJ-Adropstoapproximately70˚C/W.TheθJ-AvaluesfortheLLPpackagearealsodependentontracearea,copperthickness,andthenumberofthermalviasused(refertoapplicationnoteAN-1187).Ifpowerdisspationcausesthejunctiontemperaturetoexceedspecifiedlimits,thedevicewillgointothermalshutdown.

Note3:ESDistestedusingthehumanbodymodelwhichisa100pFcapacitordischargedthrougha1.5kresistorintoeachpin.Note4:Typicalnumbersrepresentthemostlikelyparametricnormfor25˚Coperation.

Note5:Ifusedinadual-supplysystemwheretheregulatorloadisreturnedtoanegativesupply,theoutputpinmustbediodeclampedtoground.Note6:Outputvoltagelineregulationisdefinedasthechangeinoutputvoltagefromnominalvalueresultingfromachangeininputvoltage.

Note7:Outputvoltageloadregulationisdefinedasthechangeinoutputvoltagefromnominalvalueastheloadcurrentincreasesfrom1mAtofullload.Note8:Dropoutvoltageisdefinedastheminimuminputtooutputdifferentialrequiredtomaintaintheoutputwithin100mVofnominalvalue.

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LP38690-ADJ/LP38692-ADJBlockDiagrams

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FIGURE1.LP38690-ADJFunctionalDiagram(LLP)

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FIGURE2.LP38692-ADJFunctionalDiagram(SOT-223,LLP)

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LP38690-ADJ/LP38692-ADJTypicalPerformanceCharacteristics

enablepinistiedtoVINNoisevsFrequency

Unlessotherwisespecified:TJ=25˚C,CIN=COUT=10µF,

(LP38692-ADJonly),VO=1.25V,VIN=2.7V,IL=10mA.

NoisevsFrequency

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NoisevsFrequencyRippleRejection

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RippleRejectionRippleRejection

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LP38690-ADJ/LP38692-ADJTypicalPerformanceCharacteristicsUnlessotherwisespecified:TJ=25˚C,CIN=COUT=10µF,

enablepinistiedtoVIN(LP38692-ADJonly),VO=1.25V,VIN=2.7V,IL=10mA.(Continued)

VADJvsTemperature

LineTransientResponse

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LineTransientResponseLineTransientResponse

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LineTransientResponseLineTransientResponse

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LP38690-ADJ/LP38692-ADJTypicalPerformanceCharacteristicsUnlessotherwisespecified:TJ=25˚C,CIN=COUT=10µF,

enablepinistiedtoVIN(LP38692-ADJonly),VO=1.25V,VIN=2.7V,IL=10mA.(Continued)

LineTransientResponse

LoadTransientResponse

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LoadTransientResponseLoadTransientResponse

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LoadTransientResponseLoadTransientResponse

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LP38690-ADJ/LP38692-ADJTypicalPerformanceCharacteristicsUnlessotherwisespecified:TJ=25˚C,CIN=COUT=10µF,

enablepinistiedtoVIN(LP38692-ADJonly),VO=1.25V,VIN=2.7V,IL=10mA.(Continued)

MinimumVINvsIOUTDropoutVoltagevsIOUT20126750

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EnableVoltagevsTemperatureLoadRegulationvsTemperature

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LineRegulationvsTemperature

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LP38690-ADJ/LP38692-ADJApplicationHints

EXTERNALCAPACITORS

Likeanylow-dropoutregulator,externalcapacitorsarere-quiredtoassurestability.Thesecapacitorsmustbecorrectlyselectedforproperperformance.

INPUTCAPACITOR:Aninputcapacitorofatleast1µFisrequired(ceramicrecommended).Thecapacitormustbelocatednotmorethanonecentimeterfromtheinputpinandreturnedtoacleananalogground.

OUTPUTCAPACITOR:Anoutputcapacitorisrequiredforloopstability.Itmustbelocatedlessthan1centimeterfromthedeviceandconnecteddirectlytotheoutputandgroundpinsusingtraceswhichhavenoothercurrentsflowingthroughthem.

Theminimumamountofoutputcapacitancethatcanbeusedforstableoperationis1µF.Ceramiccapacitorsarerecommended(theLP38690/2-ADJwasdesignedforusewithultralowESRcapacitors).TheLP38690/2-ADJisstablewithanyoutputcapacitorESRbetweenzeroand100Ohms.SETTINGTHEOUTPUTVOLTAGE:TheoutputvoltageissetusingtheexternalresistorsR1andR2(seeTypicalApplicationCircuit).Theoutputvoltagewillbegivenbytheequation:

VOUT=VADJX(1+R1/R2)

Becausetheparthasaminimumloadcurrentrequirementof100µA,itisrecommendedthatR2alwaysbe12kOhmsorlesstoprovideadequateloading.Evenifaminimumloadisalwaysprovidedbyothermeans,itisnotrecommendedthatveryhighvalueresistorsbeusedforR1andR2becauseitcanmaketheADJnodesusceptibletonoisepickup.Amaximumvalueof100kisrecommendedforR2topreventthisfromoccurring.

ENABLEPIN(LP38692-ADJonly):TheLP38692-ADJhasanenablepinwhichturnstheregulatoroutputonandoff.Pullingtheenablepindowntoalogiclowwillturnthepartoff.Thevoltagethepinhastobepulleduptoinordertoassurethepartisondependsoninputvoltage(refertoElectricalCharacteristicssection).ThispinshouldbetiedtoVINiftheenablefunctionisnotused.

FOLDBACKCURRENTLIMITING:Foldbackcurrentlimit-ingisbuiltintotheLP38690/2-ADJwhichreducestheamountofoutputcurrentthepartcandeliverastheoutputvoltageisreduced.TheamountofloadcurrentisdependentonthedifferentialvoltagebetweenVINandVOUT.Typically,whenthisdifferentialvoltageexceeds5V,theloadcurrentwilllimitatabout450mA.WhentheVIN-VOUTdifferentialisreducedbelow4V,loadcurrentislimitedtoabout1500mA.SELECTINGACAPACITOR

Itisimportanttonotethatcapacitancetoleranceandvaria-tionwithtemperaturemustbetakenintoconsiderationwhenselectingacapacitorsothattheminimumrequiredamountofcapacitanceisprovidedoverthefulloperatingtempera-turerange.

CapacitorCharacteristics

CERAMIC:Forvaluesofcapacitanceinthe10to100µFrange,ceramicsareusuallylargerandmorecostlythantantalumsbutgivesuperiorACperformanceforbypassinghighfrequencynoisebecauseofverylowESR(typicallylessthan10mΩ).However,somedielectrictypesdonothavegoodcapacitancecharacteristicsasafunctionofvoltageandtemperature.

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Z5UandY5Vdielectricceramicshavecapacitancethatdropsseverelywithappliedvoltage.AtypicalZ5UorY5Vcapacitorcanlose60%ofitsratedcapacitancewithhalfoftheratedvoltageappliedtoit.TheZ5UandY5Valsoexhibitaseveretemperatureeffect,losingmorethan50%ofnomi-nalcapacitanceathighandlowlimitsofthetemperaturerange.

X7RandX5Rdielectricceramiccapacitorsarestronglyrec-ommendedifceramicsareused,astheytypicallymaintainacapacitancerangewithin±20%ofnominaloverfulloperat-ingratingsoftemperatureandvoltage.Ofcourse,theyaretypicallylargerandmorecostlythanZ5U/Y5Utypesforagivenvoltageandcapacitance.

TANTALUM:SolidTantalumcapacitorshavegoodtempera-turestability:ahighqualityTantalumwilltypicallyshowacapacitancevaluethatvarieslessthan10-15%acrossthefulltemperaturerangeof-40˚Cto125˚C.ESRwillvaryonlyabout2Xgoingfromthehightolowtemperaturelimits.TheincreasingESRatlowertemperaturescancauseoscil-lationswhenmarginalqualitycapacitorsareused(iftheESRofthecapacitorisneartheupperlimitofthestabilityrangeatroomtemperature).

PCBLAYOUT

GoodPClayoutpracticesmustbeusedorinstabilitycanbeinducedbecauseofgroundloopsandvoltagedrops.Theinputandoutputcapacitorsmustbedirectlyconnectedtotheinput,output,andgroundpinsoftheregulatorusingtraceswhichdonothaveothercurrentsflowinginthem(Kelvinconnect).

ThebestwaytodothisistolayoutCINandCOUTnearthedevicewithshorttracestotheVIN,VOUT,andgroundpins.Theregulatorgroundpinshouldbeconnectedtotheexter-nalcircuitgroundsothattheregulatoranditscapacitorshavea\"singlepointground\".

Itshouldbenotedthatstabilityproblemshavebeenseeninapplicationswhere\"vias\"toaninternalgroundplanewereusedatthegroundpointsoftheICandtheinputandoutputcapacitors.Thiswascausedbyvaryinggroundpotentialsatthesenodesresultingfromcurrentflowingthroughthegroundplane.Usingasinglepointgroundtechniquefortheregulatorandit’scapacitorsfixedtheproblem.SincehighcurrentflowsthroughthetracesgoingintoVINandcomingfromVOUT,Kelvinconnectthecapacitorleadstothesepinssothereisnovoltagedropinserieswiththeinputandoutputcapacitors.

RFI/EMISUSCEPTIBILITY

RFI(radiofrequencyinterference)andEMI(electromagneticinterference)candegradeanyintegratedcircuit’sperfor-mancebecauseofthesmalldimensionsofthegeometriesinsidethedevice.Inapplicationswherecircuitsourcesarepresentwhichgeneratesignalswithsignificanthighfre-quencyenergycontent(>1MHz),caremustbetakentoensurethatthisdoesnotaffecttheICregulator.

IfRFI/EMInoiseispresentontheinputsideoftheregulator(suchasapplicationswheretheinputsourcecomesfromtheoutputofaswitchingregulator),goodceramicbypassca-pacitorsmustbeusedattheinputpinoftheIC.

IfaloadisconnectedtotheICoutputwhichswitchesathighspeed(suchasaclock),thehigh-frequencycurrentpulsesrequiredbytheloadmustbesuppliedbythecapacitorsontheICoutput.Sincethebandwidthoftheregulatorloopislessthan100kHz,thecontrolcircuitrycannotrespondto

LP38690-ADJ/LP38692-ADJApplicationHints

(Continued)

OUTPUTNOISE

Noiseisspecifiedintwoways-SpotNoiseorOutputNoisedensityistheRMSsumofallnoisesources,measuredattheregulatoroutput,ataspecificfrequency(measuredwitha1Hzbandwidth).Thistypeofnoiseisusuallyplottedonacurveasafunctionoffrequency.TotalOutputNoiseorBroad-BandNoiseistheRMSsumofspotnoiseoveraspecifiedbandwidth,usuallyseveraldecadesoffrequencies.Attentionshouldbepaidtotheunitsofmeasurement.SpotnoiseismeasuredinunitsµV/root-HzornV/root-HzandtotaloutputnoiseismeasuredinµV(rms)

Theprimarysourceofnoiseinlow-dropoutregulatorsistheinternalreference.Noisecanbereducedintwoways:byincreasingthetransistorareaorbyincreasingthecurrentdrawnbytheinternalreference.Increasingtheareawilldecreasethechanceoffittingthedieintoasmallerpackage.Increasingthecurrentdrawnbytheinternalreferencein-creasesthetotalsupplycurrent(groundpincurrent).

loadchangesabovethatfrequency.ThismeanstheeffectiveoutputimpedanceoftheICatfrequenciesabove100kHzisdeterminedonlybytheoutputcapacitor(s).

Inapplicationswheretheloadisswitchingathighspeed,theoutputoftheICmayneedRFisolationfromtheload.Itisrecommendedthatsomeinductancebeplacedbetweentheoutputcapacitorandtheload,andgoodRFbypasscapaci-torsbeplaceddirectlyacrosstheload.

PCBlayoutisalsocriticalinhighnoiseenvironments,sinceRFI/EMIiseasilyradiateddirectlyintoPCtraces.Noisycircuitryshouldbeisolatedfrom\"clean\"circuitswherepos-sible,andgroundedthroughaseparatepath.AtMHzfre-quencies,groundplanesbegintolookinductiveandRFI/EMIcancausegroundbounceacrossthegroundplane.Inmulti-layerPCBapplications,careshouldbetakeninlayoutsothatnoisypowerandgroundplanesdonotradiatedirectlyintoadjacentlayerswhichcarryanalogpowerandground.

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LP38690-ADJ/LP38692-ADJPhysicalDimensions

inches(millimeters)unlessotherwisenoted

6-lead,LLPPackage

NSPackageNumberSDE06A

SOT-223Package

NSPackageNumberMP05A

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LP38690-ADJ/LP38692-ADJ1ALowDropoutCMOSLinearRegulatorswithAdjustableOutputStablewithCeramicOutputCapacitorsNotes

Nationaldoesnotassumeanyresponsibilityforuseofanycircuitrydescribed,nocircuitpatentlicensesareimpliedandNationalreservestherightatanytimewithoutnoticetochangesaidcircuitryandspecifications.Forthemostcurrentproductinformationvisitusatwww.national.com.LIFESUPPORTPOLICY

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1.Lifesupportdevicesorsystemsaredevicesorsystemswhich,(a)areintendedforsurgicalimplantintothebody,or(b)supportorsustainlife,andwhosefailuretoperformwhenproperlyusedinaccordancewithinstructionsforuseprovidedinthelabeling,canbereasonablyexpectedtoresultinasignificantinjurytotheuser.BANNEDSUBSTANCECOMPLIANCE

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2.Acriticalcomponentisanycomponentofalifesupportdeviceorsystemwhosefailuretoperformcanbereasonablyexpectedtocausethefailureofthelifesupportdeviceorsystem,ortoaffectitssafetyoreffectiveness.