LM2727资料

LM2727/LM2737N-ChannelFETSynchronousBuckRegulatorControllerforLowOutputVoltagesJune2003

LM2727/LM2737

N-ChannelFETSynchronousBuckRegulatorControllerforLowOutputVoltages

GeneralDescription

TheLM2727andLM2737arehigh-speed,synchronous,switchingregulatorcontrollers.Theyareintendedtocontrolcurrentsof0.7Ato20Awithupto95%conversionefficien-cies.TheLM2727employsoutputover-voltageandunder-voltagelatch-off.Forapplicationswherelatch-offisnotde-sired,theLM2737canbeused.Powerupanddownsequencingisachievedwiththepower-goodflag,adjustablesoft-startandoutputenablefeatures.TheLM2737andLM2737operatefromalow-current5Vbiasandcanconvertfroma2.2Vto16Vpowerrail.Bothpartsutilizeafixed-frequency,voltage-mode,PWMcontrolarchitectureandtheswitchingfrequencyisadjustablefrom50kHzto2MHzbyadjustingthevalueofanexternalresistor.Currentlimitisachievedbymonitoringthevoltagedropacrosstheon-resistanceofthelow-sideMOSFET,whichenhanceslowduty-cycleoperation.Thewiderangeofoperatingfrequen-ciesgivesthepowersupplydesignertheflexibilitytofine-tunecomponentsize,cost,noiseandefficiency.Theadap-tive,non-overlappingMOSFETgate-driversandhigh-sidebootstrapstructurehelpstofurthermaximizeefficiency.Thehigh-sidepowerFETdrainvoltagecanbefrom2.2Vto16Vandtheoutputvoltageisadjustabledownto0.6V.

Features

nInputpowerfrom2.2Vto16V

nOutputvoltageadjustabledownto0.6V

nPowerGoodflag,adjustablesoft-startandoutputenableforeasypowersequencing

nOutputover-voltageandunder-voltagelatch-off(LM2727)

nOutputover-voltageandunder-voltageflag(LM2737)nReferenceAccuracy:1.5%(0˚C-125˚C)nCurrentlimitwithoutsenseresistornSoftstart

nSwitchingfrequencyfrom50kHzto2MHznTSSOP-14package

Applications

nnnnn

CableModems

Set-TopBoxes/HomeGatewaysDDRCorePower

High-EfficiencyDistributedPowerLocalRegulationofCorePower

TypicalApplication

20049410

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LM2727/LM2737ConnectionDiagram

20049411

14-LeadPlasticTSSOP

θJA=155˚C/W

NSPackageNumberMTC14

PinDescription

BOOT(Pin1)-SupplyrailfortheN-channelMOSFETgatedrive.Thevoltageshouldbeatleastonegatethresholdabovetheregulatorinputvoltagetoproperlyturnonthehigh-sideN-FET.

LG(Pin2)-Gatedriveforthelow-sideN-channelMOSFET.ThissignalisinterlockedwithHGtoavoidshoot-throughproblems.

PGND(Pins3,13)-GroundforFETdrivecircuitry.Itshouldbeconnectedtosystemground.

SGND(Pin4)-Groundforsignallevelcircuitry.Itshouldbeconnectedtosystemground.

VCC(Pin5)-Supplyrailforthecontroller.

PWGD(Pin6)-PowerGood.Thisisanopendrainoutput.ThepinispulledlowwhenthechipisinUVP,OVP,orUVLOmode.Duringnormaloperation,thispinisconnectedtoVCCorothervoltagesourcethroughapull-upresistor.

ISEN(Pin7)-Currentlimitthresholdsetting.Thissourcesafixed50µAcurrent.Aresistorofappropriatevalueshouldbeconnectedbetweenthispinandthedrainofthelow-sideFET.

EAO(Pin8)-Outputoftheerroramplifier.Thevoltagelevelonthispiniscomparedwithaninternallygeneratedrampsignaltodeterminethedutycycle.Thispinisnecessaryforcompensatingthecontrolloop.

SS(Pin9)-Softstartpin.Acapacitorconnectedbetweenthispinandgroundsetsthespeedatwhichtheoutputvoltagerampsup.Largercapacitorvalueresultsinsloweroutputvoltagerampbutalsolowerinrushcurrent.

FB(Pin10)-Thisistheinvertinginputoftheerroramplifier,whichisusedforsensingtheoutputvoltageandcompen-satingthecontrolloop.

FREQ(Pin11)-Theswitchingfrequencyissetbyconnect-ingaresistorbetweenthispinandground.

SD(Pin12)-ICLogicShutdown.Whenthispinispulledlowthechipturnsoffthehighsideswitchandturnsonthelowsideswitch.Whilethispinislow,theICwillnotstartup.Aninternal20µApull-upconnectsthispintoVCC.

HG(Pin14)-Gatedriveforthehigh-sideN-channelMOS-FET.ThissignalisinterlockedwithLGtoavoidshoot-throughproblems.

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LM2727/LM2737AbsoluteMaximumRatings

(Note1)InfraredorConvection(20sec)ESDRating

235˚C2kV

IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.VCCBOOTV

JunctionTemperatureStorageTemperatureSolderingInformationLeadTemperature(soldering,10sec)

260˚C7V21V150˚C

−65˚Cto150˚C

OperatingRatings

SupplyVoltage(VCC)JunctionTemperatureRangeThermalResistance(θJA)

4.5Vto5.5V−40˚Cto+125˚C

155˚C/W

ElectricalCharacteristics

VCC=5Vunlessotherwiseindicated.TypicalsandlimitsappearinginplaintypeapplyforTA=TJ=+25˚C.LimitsappearinginboldfacetypeapplyoverfullOperatingTemperatureRange.Datasheetmin/maxspecificationlimitsareguaranteedbydesign,test,orstatisticalanalysis.Symbol

Parameter

Conditions

VCC=4.5V,0˚Cto+125˚CVCC=5V,0˚Cto+125˚C

VFB_ADJFBPinVoltage

VCC=5.5V,0˚Cto+125˚CVCC=4.5V,−40˚Cto+125˚CVCC=5V,−40˚Cto+125˚CVCC=5.5V,−40˚Cto+125˚C

VONUVLOThresholds

RisingFalling

SD=5V,FB=0.55VFsw=600kHzSD=5V,FB=0.65VFsw=600kHzSD=0V

FBVoltageGoingUpFBVoltageGoingDownSSVoltage=2.5V0˚Cto+125˚C-40˚Cto+125˚C

10.80.15Min0.5910.5910.5910.50.50.5

Typ0.60.60.60.60.60..23.61.51.70.46620

85

111195

3528

5050

656515152

mA

2.20.7

mAµsµsµAµA

Max0.6090.6090.6090.6090.6090.609

VVUnits

IQ-V5OperatingVCCCurrent

ShutdownVCCCurrent

tPWGD1tPWGD2ISDISS-ONPWGDPinResponseTimePWGDPinResponseTimeSDPinInternalPull-upCurrentSSPinSourceCurrent

ISS-OCSSPinSinkCurrentDuringOverSSVoltage=2.5VCurrent

ISENPinSourceCurrentTripPoint

ErrorAmplifierUnityGainBandwidth

ErrorAmplifierDCGainErrorAmplifierSlewRateFBPinBiasCurrent

EAOPinCurrentSourcingandSinking

ErrorAmplifierMaximumSwing

FB=0.55VFB=0.65V

VEAO=2.5,FB=0.55VVEAO=2.5,FB=0.65VMinimumMaximum

00

0˚Cto+125˚C-40˚Cto+125˚C

µAµA

ISEN-THERRORAMPLIFIER

GBWGSRIFBIEAOVEA560615302.80.81.23.2

100155

MHzdBV/µAnAmAV

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LM2727/LM2737ElectricalCharacteristics

(Continued)

VCC=5Vunlessotherwiseindicated.TypicalsandlimitsappearinginplaintypeapplyforTA=TJ=+25˚C.LimitsappearinginboldfacetypeapplyoverfullOperatingTemperatureRange.Datasheetmin/maxspecificationlimitsareguaranteedbydesign,test,orstatisticalanalysis.Symbol

Parameter

BOOTPinQuiescentCurrent

Conditions

BOOTV=12V,EN=00˚Cto+125˚C-40˚Cto+125˚CBOOT-SW=5V@350mABOOT-SW=5V@350mABOOT-SW=5V@350mABOOT-SW=5V@350mA

Min

Typ

Max

Units

GATEDRIVEIQ-BOOT95953232

160215

µA

RDS1RDS2RDS3RDS4OSCILLATOR

TopFETDriverPull-UpONresistance

TopFETDriverPull-DownONresistance

BottomFETDriverPull-UpONresistance

BottomFETDriverPull-DownONresistance

ΩΩΩΩ

RFADJ=590kΩRFADJ=88.7kΩ

fOSCPWMFrequency

RFADJ=42.2kΩ,0˚Cto+125˚CRFADJ=42.2kΩ,-40˚Cto+125˚CRFADJ=17.4kΩRFADJ=11.3kΩ

D

MaxDutyCycle

fPWM=300kHzfPWM=600kHz

500490

503006006001400200090882.6

3.5

%

700700

kHz

LOGICINPUTSANDOUTPUTS

VSD-IHVSD-ILVPWGD-TH-LOSDPinLogicHighTripPointSDPinLogicLowTripPointPWGDPinTripPoints

0˚Cto+125˚C-40˚Cto+125˚CFBVoltageGoingDown0˚Cto+125˚C-40˚Cto+125˚CFBVoltageGoingUp0˚Cto+125˚C-40˚Cto+125˚C

1.31.250.4130.4100.6910.688

VV

1.61.60.4300.4300.7100.71035110

0.4460.4460.7340.734

V

VPWGD-TH-HIPWGDPinTripPoints

V

VPWGD-HYSPWGDHysteresis(LM2737only)FBVoltageGoingDownFBVoltage

GoingUp

mV

Note1:Absolutemaximumratingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.Operatingratingsindicateconditionsforwhichthedeviceoperatescorrectly.OpeartingRatingsdonotimplyguaranteedperformancelimits.

Note2:Thehumanbodymodelisa100pFcapacitordischargedthrougha1.5kresistorintoeachpin.

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LM2727/LM2737TypicalPerformanceCharacteristics

Efficiency(VO=1.5V)FSW=300kHz,TA=25˚C

Efficiency(VO=3.3V)FSW=300kHz,TA=25˚C

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VCCOperatingCurrentvsTemperature

FSW=600kHz,No-LoadBootpinCurrentvsTemperatureforBOOTV=12V

FSW=600kHz,Si4826DYFET,No-Load

20049415

20049414

BootpinCurrentvsTemperaturewith5VBootstrap

FSW=600kHz,Si4826DYFET,No-LoadPWMFrequencyvsTemperature

forRFADJ=43.2kΩ

20049416

20049417

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LM2727/LM2737TypicalPerformanceCharacteristics

RFADJvsPWMFrequency

(in100to800kHzrange),TA=25˚C

(Continued)

RFADJvsPWMFrequency

(in900to2000kHzrange),TA=25˚C

2004941820049419

VCCOperatingCurrentPlusBootCurrentvsPWMFrequency(Si4826DYFET,TA=25˚C)

SwitchWaveforms(HGFalling)

VIN=5V,VO=1.8VIO=3A,CSS=10nFFSW=600kHz

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20049420

SwitchWaveforms(HGRising)

VIN=5V,VO=1.8VIO=3A,FSW=600kHz

Start-Up(No-Load)VIN=10V,VO=1.2VCSS=10nF,FSW=300kHz

2004942420049421

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LM2727/LM2737TypicalPerformanceCharacteristics

Start-Up(Full-Load)VIN=10V,VO=1.2VIO=10A,CSS=10nF

FSW=300kHz

(Continued)

StartUp(No-Load,10xCSS)

VIN=10V,VO=1.2VCSS=100nF,FSW=300kHz

2004942220049426

StartUp(FullLoad,10xCSS)

VIN=10V,VO=1.2VIO=10A,CSS=100nF

FSW=300kHzShutdown

VIN=10V,VO=1.2VIO=10A,CSS=10nF

FSW=300kHz

2004942520049427

StartUp(FullLoad,10xCSS)

VIN=10V,VO=1.2VIO=10A,CSS=100nF

FSW=300kHz

LoadTransientResponse(IO=0to4A)

VIN=12V,VO=1.2V

FSW=300kHz

2004943320049428

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LM2727/LM2737TypicalPerformanceCharacteristics

LoadTransientResponse(IO=4to0A)

VIN=12V,VO=1.2V

FSW=300kHz

(Continued)

LineTransientResponse(VIN=5Vto12V)

VO=1.2V,IO=5AFSW=300kHz

2004942920049430

LineTransientResponse(VIN=12Vto5V)

VO=1.2V,IO=5AFSW=300kHzLineTransientResponse

VO=1.2V,IO=5AFSW=300kHz

2004943120049432

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LM2727/LM2737BlockDiagram

20049401

ApplicationInformation

THEORYOFOPERATION

TheLM2727isavoltage-mode,high-speedsynchronousbuckregulatorwithaPWMcontrolscheme.Itisdesignedforuseinset-topboxes,thinclients,DSL/Cablemodems,andotherapplicationsthatrequirehighefficiencybuckconvert-ers.Ithaspowergood(PWRGD),outputshutdown(SD),overvoltageprotection(OVP)andundervoltageprotection(UVP).Theover-voltageandunder-voltagesignalsareORgatedtodrivethePowerGoodsignalandashutdownlatch,whichturnsoffthehighsidegateandturnsonthelowsidegateifpulledlow.CurrentlimitisachievedbysensingthevoltageVDSacrossthelowsideFET.Duringcurrentlimitthehighsidegateisturnedoffandthelowsidegateturnedon.Thesoftstartcapacitorisdischargedbya95µAsource(reducingthemaximumdutycycle)untilthecurrentisundercontrol.TheLM2737doesnotlatchoffduringUVPorOVP,andusestheHIGHandLOWcomparatorsforthepower-goodfunctiononly.

STARTUP

WhenVCCexceeds4.2VandtheenablepinENseesalogichighthesoftstartcapacitorbeginschargingthroughaninternalfixed10µAsource.Duringthistimetheoutputoftheerroramplifierisallowedtorisewiththevoltageofthesoftstartcapacitor.Thiscapacitor,Css,determinessoftstarttime,andcanbedeterminedapproximatelyby:

9

Anapplicationforamicroprocessormightneedadelayof3ms,inwhichcaseCSSwouldbe12nF.Foradifferentdevice,a100msdelaymightbemoreappropriate,inwhichcaseCSSwouldbe400nF.(39010%)DuringsoftstartthePWRGDflagisforcedlowandisreleasedwhenthevoltagereachesasetvalue.Atthispointthischipentersnormaloperationmode,thePowerGoodflagisreleased,andtheOVPandUVPfunctionsbegintomonitorVo.

NORMALOPERATION

Whileinnormaloperationmode,theLM2727/37regulatestheoutputvoltagebycontrollingthedutycycleofthehighsideandlowsideFETs.Theequationgoverningoutputvoltageis:

ThePWMfrequencyisadjustablebetween50kHzand2MHzandissetbyanexternalresistor,RFADJ,betweentheFREQpinandground.Theresistanceneededforadesiredfrequencyisapproximately:

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LM2727/LM2737ApplicationInformation

(Continued)

untilVCCrisesabove4.2V.Aswithshutdown,thesoftstartcapacitorisdischargedthroughaFET,ensuringthatthenextstart-upwillbesmooth.CURRENTLIMIT

MOSFETGATEDRIVERS

TheLM2727/37hastwogatedriversdesignedfordrivingN-channelMOSFETsinasynchronousmode.PowerforthedriversissuppliedthroughtheBOOTVpin.Forthehighsidegate(HG)tofullyturnonthetopFET,theBOOTVvoltagemustbeatleastoneVGS(th)greaterthanVin.(BOOTV≥2*Vin)Thisvoltagecanbesuppliedbyaseparate,highervoltagesource,orsuppliedfromalocalchargepumpstruc-ture.Inasystemsuchasadesktopcomputer,both5Vand12Vareusuallyavailable.HenceifVinwas5V,the12VsupplycouldbeusedforBOOTV.12Vismorethan2*Vin,sotheHGwouldoperatecorrectly.ForaBOOTVof12V,theinitialgatechargingcurrentis2A,andtheinitialgatedis-chargingcurrentistypically6A.

CurrentlimitisrealizedbysensingthevoltageacrossthelowsideFETwhileitison.TheRDSONoftheFETisaknownvalue,hencethecurrentthroughtheFETcanbedeterminedas:

VDS=I*RDSONThecurrentlimitisdeterminedbyanexternalresistor,RCS,connectedbetweentheswitchnodeandtheISENpin.Aconstantcurrentof50µAisforcedthroughRcs,causingafixedvoltagedrop.ThisfixedvoltageiscomparedagainstVDSandifthelatterishigher,thecurrentlimitofthechiphasbeenreached.RCScanbefoundbyusingthefollowing:

RCS=RDSON(LOW)*ILIM/50µA

Forexample,aconservative15Acurrentlimitina10AdesignwithaminimumRDSONof10mΩwouldrequirea3.3kΩresistor.BecausecurrentsensingisdoneacrossthelowsideFET,nominimumhighsideon-timeisnecessary.InthecurrentlimitmodetheLM2727/37willturnthehighsideoffandthekeeplowsideonforaslongasnecessary.Thechipalsodischargesthesoftstartcapacitorthroughafixed95µAsource.Inthisway,smoothrampingupoftheoutputvoltageaswithanormalsoftstartisensured.TheoutputoftheLM2727/37internalerroramplifierislimitedbythevolt-ageonthesoftstartcapacitor.Hence,dischargingthesoftstartcapacitorreducesthemaximumdutycycleDofthecontroller.Duringseverecurrentlimit,thisreductionindutycyclewillreducetheoutputvoltage,ifthecurrentlimitcon-ditionslastsforanextendedtime.

Duringthefirstfewnanosecondsafterthelowsidegateturnson,thelowsideFETbodydiodeconducts.Thiscausesanadditional0.7VdropinVDS.TherangeofVDSisnormallymuchlower.Forexample,ifRDSONwere10mΩandthecurrentthroughtheFETwas10A,VDSwouldbe0.1V.Thecurrentlimitwouldsee0.7Vasa70Acurrentandentercurrentlimitimmediately.Hencecurrentlimitismaskeddur-ingthetimeittakesforthehighsideswitchtoturnoffandthelowsideswitchtoturnon.

UVP/OVP

Theoutputundervoltageprotectionandovervoltageprotec-tionmechanismsengageat70%and118%ofthetargetoutputvoltage,respectively.Ineithercase,theLM2727willturnoffthehighsideswitchandturnonthelowsideswitch,anddischargethesoftstartcapacitorthroughaMOSFETswitch.Thechipremainsinthisstateuntiltheshutdownpinhasbeenpulledtoalogiclowandthenreleased.TheUVPfunctionismaskedonlyduringthefirstchargingofthesoftstartcapacitor,whenvoltageisfirstappliedtotheVCCpin.Incontrast,theLM2737isdesignedtocontinueoperatingdur-ingUVPorOVPconditions,andtoresumenormaloperationoncethefaultconditioniscleared.AswiththeLM2727,thepowergoodflaggoeslowduringthistime,givingalogic-levelwarningsignal.

SHUTDOWN

IftheshutdownpinSDispulledlow,theLM2727/37dis-chargesthesoftstartcapacitorthroughaMOSFETswitch.Thehighsideswitchisturnedoffandthelowsideswitchisturnedon.TheLM2727/37remainsinthisstateuntilSDisreleased.

20049402

FIGURE1.BOOTVSuppliedbyChargePumpInasystemwithoutaseparate,highervoltage,achargepump(bootstrap)canbebuiltusingadiodeandsmallca-pacitor,Figure1.ThecapacitorservestomaintainenoughvoltagebetweenthetopFETgateandsourcetocontrolthedeviceevenwhenthetopFETisonanditssourcehasrisenuptotheinputvoltagelevel.

TheLM2727/37gatedrivesuseaBiCMOSdesign.UnlikesomeotherbipolarcontrolICs,thegatedrivershaverail-to-railswing,ensuringnospuriousturn-onduetocapacitivecoupling.

POWERGOODSIGNAL

Thepowergoodsignalistheor-gatedflagrepresentingover-voltageandunder-voltageprotection.Iftheoutputvolt-ageis18%overit’snominalvalue,VFB=0.7V,orfalls30%belowthatvalue,VFB=0.41V,thepowergoodflaggoeslow.Theconverterthenturnsoffthehighsidegate,andturnsonthelowsidegate.Unliketheoutput(LM2727only)thepowergoodflagisnotlatchedoff.Itwillreturntoalogichighwheneverthefeedbackpinvoltageisbetween70%and118%of0.6V.

UVLO

The4.2Vturn-onthresholdonVCChasabuiltinhysteresisof0.6V.Therefore,ifVCCdropsbelow3.6V,thechipentersUVLOmode.UVLOconsistsofturningoffthetopFET,turningonthebottomFET,andremaininginthatcondition

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LM2727/LM2737ApplicationInformation

DESIGNCONSIDERATIONS

(Continued)

ThefollowingisadesignprocedureforallthecomponentsneededtocreatethecircuitshowninFigure3intheEx-ampleCircuitssection,a5Vinto1.2Voutconverter,capableofdelivering10Awithanefficiencyof85%.Theswitchingfrequencyis300kHz.ThesameprocedurescanbefollowedtocreatethecircuitshowninFigure3,Figure4,andtocreatemanyotherdesignswithvaryinginputvoltages,out-putvoltages,andoutputcurrents.

INPUTCAPACITOR

TheinputcapacitorsinaBuckswitchingconverteraresub-jectedtohighstressduetotheinputcurrentwaveform,whichisasquarewave.HenceinputcapsareselectedfortheirripplecurrentcapabilityandtheirabilitytowithstandtheheatgeneratedasthatripplecurrentrunsthroughtheirESR.Inputrmsripplecurrentisapproximately:

Inthecaseofadesktopcomputersystem,theinputcurrentslewrateisthesystempowersupplyor\"silverbox\"outputcurrentslewrate,whichistypicallyabout0.1A/µs.TotalinputcapacitorESRis9mΩ,hence∆Vis10*0.009=90mV,andtheminimuminductancerequiredis0.9µH.Theinputinduc-torshouldberatedtohandletheDCinputcurrent,whichisapproximatedby:

InthiscaseIIN-DCisabout2.8A.OnepossiblechoiceistheTDKSLF12575T-1R2N8R2,a1.2µHdevicethatcanhandle8.2Arms,andhasaDCRof7mΩ.

OUTPUTINDUCTOR

TheoutputinductorformsthefirsthalfofthepowerstageinaBuckconverter.Itisresponsibleforsmoothingthesquarewavecreatedbytheswitchingactionandforcontrollingtheoutputcurrentripple.(∆Io)Theinductanceischosenbyselectingbetweentradeoffsinefficiencyandresponsetime.Thesmallertheoutputinductor,themorequicklythecon-vertercanrespondtotransientsintheloadcurrent.Asshownintheefficiencycalculations,however,asmallerin-ductorrequiresahigherswitchingfrequencytomaintainthesamelevelofoutputcurrentripple.AnincreaseinfrequencycanmeanincreasinglossintheFETsduetothecharginganddischargingofthegates.Generallytheswitchingfre-quencyischosensothatconductionlossoutweighsswitch-ingloss.Theequationforoutputinductorselectionis:

Thepowerdissipatedbyeachinputcapacitoris:

Here,nisthenumberofcapacitors,andindicatesthatpowerlossineachcapdecreasesrapidlyasthenumberofinputcapsincrease.Theworst-caserippleforaBuckconverteroccursduringfullload,whenthedutycycleD=50%.Inthe5Vto1.2Vcase,D=1.2/5=0.24.Witha10Amaximumloadtheripplecurrentis4.3A.TheSanyo10MV5600AXaluminumelectrolyticcapacitorhasaripplecurrentratingof2.35A,upto105˚C.Twosuchcapacitorsmakeaconservativedesignthatallowsforunequalcurrentsharingbetweenindividualcaps.Eachcapacitorhasamaxi-mumESRof18mΩat100kHz.Powerlossineachdeviceisthen0.05W,andtotallossis0.1W.OtherpossibilitiesforinputandoutputcapacitorsincludeMLCC,tantalum,OSCON,SP,andPOSCAPS.

INPUTINDUCTOR

Theinputinductorservestwobasicpurposes.First,inhighpowerapplications,theinputinductorhelpsinsulatetheinputpowersupplyfromswitchingnoise.Thisisespeciallyimportantifotherswitchingconvertersdrawcurrentfromthesamesupply.Noiseathighfrequency,suchasthatdevel-opedbytheLM2727at1MHzoperation,couldpassthroughtheinputstageofaslowerconverter,contaminatingandpossiblyinterferingwithitsoperation.

AninputinductoralsohelpsshieldtheLM2727fromhighfrequencynoisegeneratedbyotherswitchingconverters.Thesecondpurposeoftheinputinductoristolimittheinputcurrentslewrate.Duringachangefromno-loadtofull-load,theinputinductorseesthehighestvoltagechangeacrossit,equaltothefullloadcurrenttimestheinputcapacitorESR.Thisvaluedividedbythemaximumallowableinputcurrentslewrategivestheminimuminputinductance:

Plugginginthevaluesforoutputcurrentripple,inputvoltage,outputvoltage,switchingfrequency,andassuminga40%peak-to-peakoutputcurrentrippleyieldsaninductanceof1.5µH.Theoutputinductormustberatedtohandlethepeakcurrent(alsoequaltothepeakswitchcurrent),whichis(Io+0.5*∆Io).Thisis12Afora10Adesign.TheCoilcraftD05022-152HCis1.5µH,isratedto15Arms,andhasaDCRof4mΩ.OUTPUTCAPACITOR

TheoutputcapacitorformsthesecondhalfofthepowerstageofaBuckswitchingconverter.Itisusedtocontroltheoutputvoltageripple(∆Vo)andtosupplyloadcurrentduringfastloadtransients.

Inthisexampletheoutputcurrentis10Aandtheexpectedtypeofcapacitorisanaluminumelectrolytic,aswiththeinputcapacitors.(Otherpossibilitiesincludeceramic,tanta-lum,andsolidelectrolytecapacitors,howevertheceramictypeoftendonothavethelargecapacitanceneededtosupplycurrentforloadtransients,andtantalumstendtobemoreexpensivethanaluminumelectrolytic.)Aluminumca-pacitorstendtohaveveryhighcapacitanceandfairlylowESR,meaningthattheESRzero,whichaffectssystemstability,willbemuchlowerthantheswitchingfrequency.Thelargecapacitancemeansthatatswitchingfrequency,theESRisdominant,hencethetypeandnumberofoutputcapacitorsisselectedonthebasisofESR.OnesimpleformulatofindthemaximumESRbasedonthedesiredoutputvoltageripple,∆Voandthedesignedoutputcurrentripple,∆Io,is:

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LM2727/LM2737ApplicationInformation

(Continued)

Inthisexample,inordertomaintaina2%peak-to-peakoutputvoltagerippleanda40%peak-to-peakinductorcur-rentripple,therequiredmaximumESRis6mΩ.ThreeSanyo10MV5600AXcapacitorsinparallelwillgiveanequivalentESRof6mΩ.Thetotalbulkcapacitanceof16.8mFisenoughtosupplyevensevereloadtransients.Usingthesamecapacitorsforbothinputandoutputalsokeepsthebillofmaterialssimple.MOSFETS

MOSFETSareacriticalpartofanyswitchingcontrollerandhaveadirectimpactonthesystemefficiency.Inthiscasethetargetefficiencyis85%andthisisthevariablethatwilldeterminewhichdevicesareacceptable.Lossfromtheca-pacitors,inductors,andtheLM2727itselfaredetailedintheEfficiencysection,andcometoabout0.54W.Tomeetthetargetefficiency,thisleaves1.45WfortheFETconductionloss,gatechargingloss,andswitchingloss.Switchinglossisparticularlydifficulttoestimatebecauseitdependsonmanyfactors.Whentheloadcurrentismorethanabout1or2amps,conductionlossesoutweightheswitchingandgatecharginglosses.ThisallowsFETselectionbasedontheRDSONoftheFET.AddingtheFETswitchingandgate-charginglossestotheequationleaves1.2Wforconductionlosses.Theequationforconductionlossis:

PCnd=D(I2o*RDSON*k)+(1-D)(I2o*RDSON*k)

ThefactorkisaconstantwhichisaddedtoaccountfortheincreasingRDSONofaFETduetoheating.Here,k=1.3.TheSi4442DYhasatypicalRDSONof4.1mΩ.WhenpluggedintotheequationforPCNDtheresultisalossof0.533W.Ifthisdesignwerefora5Vto2.5Vcircuit,anequalnumberofFETsonthehighandlowsideswouldbethebestsolution.WiththedutycycleD=0.24,itbecomesapparentthatthelowsideFETcarriestheloadcurrent76%ofthetime.AddingasecondFETinparalleltothebottomFETcouldimprovetheefficiencybyloweringtheeffectiveRDSON.Thelowerthedutycycle,themoreeffectiveasecondoreventhirdFETcanbe.Foraminimalincreaseingatechargingloss(0.054W)thedecreaseinconductionlossis0.15W.Whatwasan85%designimprovesto86%fortheaddedcostofoneSO-8MOSFET.

CONTROLLOOPCOMPONENTS

ThecircuitisthisdesignexampleandtheothersshownintheExampleCircuitssectionhavebeencompensatedtoimprovetheirDCgainandbandwidth.Theresultofthiscompensationisbetterlineandloadtransientresponses.FortheLM2727,thetopfeedbackdividerresistor,Rfb2,isalsoapartofthecompensation.Forthe10A,5Vto1.2Vdesign,thevaluesare:

Cc1=4.7pF10%,Cc2=1nF10%,Rc=229kΩ1%.Thesevaluesgiveaphasemarginof63˚andabandwidthof29.3kHz.

SUPPORTCAPACITORSANDRESISTORS

TheCinxcapacitorsarehighfrequencybypassdevices,designedtofilterharmonicsoftheswitchingfrequencyandinputnoise.Two1µFceramiccapacitorswithasufficientvoltagerating(10VfortheCircuitofFigure3)willworkwellinalmostanycase.

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12

RbypassandCbypassarestandardfiltercomponentsde-signedtoensuresmoothDCvoltageforthechipsupplyandforthebootstrapstructure,ifitisused.Use10Ωfortheresistoranda2.2µFceramicforthecap.Cbisthebootstrapcapacitor,andshouldbe0.1µF.(Inthecaseofaseparate,highersupplytotheBOOTVpin,this0.1µFcapcanbeusedtobypassthesupply.)UsingaSchottkydevicefortheboot-strapdiodeallowstheminimumdropforbothhighandlowsidedrivers.TheOnSemiconductorBAT54orMBR0520workwell.

Rpisastandardpull-upresistorfortheopen-drainpowergoodsignal,andshouldbe10kΩ.Ifthisfeatureisnotnecessary,itcanbeomitted.

RCSistheresistorusedtosetthecurrentlimit.Sincethedesigncallsforapeakcurrentmagnitude(Io+0.5*∆Io)of12A,asafesettingwouldbe15A.(Thisiswellbelowthesaturationcurrentoftheoutputinductor,whichis25A.)FollowingtheequationfromtheCurrentLimitsection,usea3.3kΩresistor.

RFADJisusedtosettheswitchingfrequencyofthechip.FollowingtheequationintheTheoryofOperationsection,theclosest1%toleranceresistortoobtainfSW=300kHzis88.7kΩ.

CSSdependsontheusersrequirements.BasedontheequationforCSSintheTheoryofOperationsection,fora3msdelay,a12nFcapacitorwillsuffice.

EFFICIENCYCALCULATIONS

Areasonableestimationoftheefficiencyofaswitchingcontrollercanbeobtainedbyaddingtogetherthelossiseachcurrentcarryingelementandusingtheequation:

ThefollowingshowsanefficiencycalculationtocomplementtheCircuitofFigure3.Outputpowerforthiscircuitis1.2Vx10A=12W.

ChipOperatingLoss

PIQ=IQ-VCC*VCC2mAx5V=0.01W

FETGateChargingLoss

PGC=n*VCC*QGS*fOSCThevaluenisthetotalnumberofFETsused.TheSi4442DYhasatypicaltotalgatecharge,QGS,of36nCandanrds-onof4.1mΩ.ForasingleFETontopandbottom:2*5*36E-9*300,000=0.108WFETSwitchingLoss

PSW=0.5*Vin*IO*(tr+tf)*fOSCTheSi4442DYhasatypicalrisetimetrandfalltimetfof11and47ns,respectively.0.5*5*10*58E-9*300,000=0.435W

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LM2727/LM2737ApplicationInformation

FETConductionLoss

PCn=0.533W

InputCapacitorLoss

(Continued)

InputInductorLoss

PLin=I2in*DCRinput-L2.822*0.007=0.055W

OutputInductorLoss

PLout=I2o*DCRoutput-L102*0.004=0.4WSystemEfficiency

4.282*0.018/2=0.084W

ExampleCircuits

20049403

FIGURE2.5V-16Vto3.3V,10A,300kHz

Thiscircuitandtheonefeaturedonthefrontpagehavebeendesignedtodeliverhighcurrentandhighefficiencyinasmallpackage,bothinareaandinheightThetallestcomponentin

thiscircuitistheinductorL1,whichis6mmtall.Thecom-pensationhasbeendesignedtotolerateinputvoltagesfrom5to16V.

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LM2727/LM2737ExampleCircuits

(Continued)

20049404

FIGURE3.5Vto1.2V,10A,300kHz

Thiscircuitdesign,detailedintheDesignConsiderationssection,usesinexpensivealuminumcapacitorsandoff-the-shelfinductors.Itcandeliver10Aatbetterthan85%effi-ciency.Largebulkcapacitanceoninputandoutputensurestableoperation.

20049405

FIGURE4.5Vto1.8V,3A,600kHz

TheexamplecircuitofFigure4hasbeendesignedforminimumcomponentcountandoverallsolutionsize.Aswitchingfrequencyof600kHzallowstheuseofsmallinput/outputcapacitorsandasmallinductor.Theavailabilityofseparate5Vand12Vsupplies(suchasthoseavailablefromdesk-topcomputersupplies)andthelowcurrentfurther

reducecomponentcount.Usingthe12VsupplytopowertheMOSFETdriverseliminatesthebootstrapdiode,D1.Atlowcurrents,smallerFETsordualFETsareoftenthemostefficientsolutions.Here,theSi4826DY,anasymmetricdualFETinanSO-8package,yields92%efficiencyataloadof2A.

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LM2727/LM2737ExampleCircuits

(Continued)

20049406

FIGURE5.3.3Vto0.8V,5A,500kHz

ThecircuitofFigure5demonstratestheLM2727deliveringalowoutputvoltageathighefficiency(87%)Aseparate5Vsupplyisrequiredtorunthechip,howevertheinputvoltagecanbeaslowas2.2

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LM2727/LM2737ExampleCircuits

(Continued)

20049407

FIGURE6.1.8Vand3.3V,1A,1.4MHz,Simultaneous

ThecircuitsinFigure6areintendedforADSLapplications,wherethehighswitchingfrequencykeepsnoiseoutofthedatatransmissionrange.Inthisdesign,the1.8and3.3Voutputscomeupsimultaneouslybyusingthesamesoftstartcapacitor.Becausetwocurrentsourcesnowchargethesamecapacitor,thecapacitancemustbedoubledtoachievethesamesoftstarttime.(Here,40nFisusedtoachievea

5mssoftstarttime.)Acommonsoftstartcapacitormeansthat,shouldonecircuitentercurrentlimit,theothercircuitwillalsoentercurrentlimit.Inaddition,ifbothcircuitsarebuiltwiththeLM2727,aUVPorOVPfaultononecircuitwillcausebothcircuitstolatchoff.TheadditionalcompensationcomponentsRc2andCc3areneededforthelowESR,allceramicoutputcapacitors,andthewide(3x)rangeofVin.

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LM2727/LM2737ExampleCircuits

(Continued)

20049408

FIGURE7.12VUnregulatedto3.3V,3A,750kHz

ThiscircuitshowstheLM27x7pairedwithacosteffectivesolutiontoprovidethe5Vchippowersupply,usingnoextracomponentsotherthantheLM78L05regulatoritself.Theinputvoltagecomesfroma’brick’powersupplywhichdoes

notregulatethe12Vlinetightly.Additional,inexpensive10uFceramiccapacitors(CinxandCox)helpisolatedeviceswithsensitivedatabands,suchasDSLandcablemodems,fromswitchingnoiseandharmonics.

20049409

FIGURE8.12Vto5V,1.8A,100kHz

Insituationswherelowcostisveryimportant,theLM27x7canalsobeusedasanasynchronouscontroller,asshownintheabovecircuit.AlthoughaaschottkydiodeinplaceofthebottomFETwillnotbeasefficient,itwillcostmuchlessthantheFET.The5VatlowcurrentneededtoruntheLM27x7couldcomefromazenerdiodeorinexpensiveregulator,

17

suchastheoneshowninFigure7.BecausetheLM27x7sensescurrentinthelowsideMOSFET,thecurrentlimitfeaturewillnotfunctioninanasynchronousdesign.TheISENpinshouldbeleftopeninthiscase.

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LM2727/LM2737TABLE1.BillofMaterialsforTypicalApplicationCircuit

IDU1Q1,Q2L1Cin1,Cin2CinxCo1,Co2CbootCinCssCc1Cc2RinRfadjRc1Rfb1Rfb2Rcs

PartNumberLM2727Si4884DYRLF7030T-1R5N6R1C2012X5R1J106MC3216X7R1E105K6MV2200WGVJ1206X104XXAC3216X7R1E225KVJ1206X123KXXVJ1206A2R2KXXVJ1206A181KXXCRCW1206100JCRCW12066342FCRCW12063923FCRCW12061002FCRCW12061002FCRCW1206222J

TypeSynchronousControllerN-MOSFETInductorMLCCCapacitorAL-ECapacitorCapacitorCapacitorCapacitorCapacitorResistorResistorResistorResistorResistorResistor

SizeTSSOP-14SO-87.1x7.1x3.2mm

0805120610mmD20mmH

12061206120612061206120612061206120612061206

ParametersTSSOP-1430V,4.1mΩ,36nC1.5µH,6.1A9.6mΩ

10µF6.3V1µF,25V2200µF6.3V125mΩ

0.1µF,25V0.1µF,25V12nF,25V2.2pF10%180pF10%10Ω5%63.4kΩ1%392kΩ1%10kΩ1%10kΩ1%2.2kΩ5%

Qty.11121211111111111

VendorNSCVishayTDKTDKTDKSanyoVishayTDKVishayVishayVishayVishayVishayVishayVishayVishayVishay

TABLE2.BillofMaterialsforCircuitofFigure2(IdenticaltoBOMfor1.5Vexceptasnotedbelow)

IDL1Co1,Co2,Co3,Co4Cc1Cc2Cc3Rc2Rfb1

PartNumberRLF12560T-2R7N110

10TPB100MVJ1206A6R8KXXVJ1206A271KXXVJ1206A471KXXCRCW12068451FCRCW12061102F

TypeInductorPOSCAPCapacitorCapacitorCapacitorResistorResistor

Size12.5x12.8x6mm7.3x4.3x2.8mm

12061206120612061206

Parameters2.7µH,14.4A4.5mΩ100µF10V1.9Arms

6.8pF10%270pF10%470pF10%8.45kΩ1%11kΩ1%

Qty.1411111

VendorTDKSanyoVishayVishayVishayVishayVishay

TABLE3.BillofMaterialsforCircuitofFigure3

IDU1Q1Q2D1LinL1Cin1,Cin2CinxCo1,Co2,Co3CbootCinCss

PartNumberLM2727Si4442DYSi4442DYBAT-54

SLF12575T-1R2N8R2D05022-152HC10MV5600AXC3216X7R1E105K10MV5600AXVJ1206X104XXAC3216X7R1E225KVJ1206X123KXX

TypeSynchronousControllerN-MOSFETN-MOSFETSchottkyDiodeInductorInductorAluminumElectrolyticCapacitorAluminumElectrolyticCapacitorCapacitorCapacitor

SizeTSSOP-14SO-8SO-8SOT-2312.5x12.5x7.5mm22.35x16.26x8mm16mmD25mmH

120616mmD25mmH

120612061206

30V,4.1mΩ,@4.5V,

36nC30V,4.1mΩ,@4.5V,

36nC

30V

12µH,8.2A,6.9mΩ1.5µH,15A,4mΩ5600µF10V2.35Arms

1µF,25V5600µF10V2.35Arms

0.1µF,25V2.2µF,25V12nF,25VParameters

Qty.111111212111

VendorNSCVishayVishayVishayCoilcraftCoilcraftSanyoTDKSanyoVishayTDKVishay

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LM2727/LM2737TABLE3.BillofMaterialsforCircuitofFigure3(Continued)

IDCc1Cc2RinRfadjRc1Rfb1Rfb2Rcs

PartNumberVJ1206A4R7KXXVJ1206A102KXXCRCW1206100JCRCW12068872FCRCW12062293FCRCW120991FCRCW120991FCRCW1206152J

TypeCapacitorCapacitorResistorResistorResistorResistorResistorResistor

Size12061206120612061206120612061206

Parameters4.7pF10%1nF10%10Ω5%88.7kΩ1%229kΩ1%4.99kΩ1%4.99kΩ1%1.5kΩ5%

Qty.11111111

VendorVishayVishayVishayVishayVishayVishayVishayVishay

TABLE4.BillofMaterialsforCircuitofFigure4

IDU1Q1/Q2L1Cin1Co1CcCinCssCc1Cc2RinRfadjRc1Rfb1Rfb2Rcs

PartNumberLM2727Si4826DYDO3316P-22210TPB100ML4TPB220MLC3216X7R1E105KC3216X7R1E225KVJ1206X123KXXVJ1206A100KXXVJ1206A561KXXCRCW1206100JCRCW120222FCRCW12065112FCRCW12062491FCRCW120991FCRCW1206272J

TypeSynchronousControllerAsymetricDualN-MOSFETInductorPOSCAPPOSCAPCapacitorCapacitorCapacitorCapacitorCapacitorResistorResistorResistorResistorResistorResistor

SizeTSSOP-14SO-812.95x9.4x5.21mm7.3x4.3x3.1mm7.3x4.3x3.1mm

12061206120612061206120612061206120612061206

30V,24mΩ/8nCTop16.5mΩ/15nC2.2µH,6.1A,12mΩ100µF10V1.9Arms220µF4V1.9Arms

1µF,25V2.2µF,25V12nF,25V10pF10%560pF10%10Ω5%42.2kΩ1%51.1kΩ1%2.49kΩ1%4.99kΩ1%2.7kΩ5%Parameters

Qty.1111111111111111

VendorNSCVishayCoilcraftSanyoSanyoTDKTDKVishayVishayVishayVishayVishayVishayVishayVishayVishay

TABLE5.BillofMaterialsforCircuitofFigure5

IDU1Q1Q2D1LinL1Cin1CinxCo1,Co2,Co3CbootCinCss

PartNumberLM2727Si4884DYSi4884DYBAT-54P1166.102TP1168.102T10MV5600AXC3216X7R1E105K16MV4700WXVJ1206X104XXAC3216X7R1E225KVJ1206X123KXX

TypeSynchronousControllerN-MOSFETN-MOSFETSchottkyDiodeInductorInductorAluminumElectrolyticCapacitorAluminumElectrolyticCapacitorCapacitorCapacitor

SizeTSSOP-14SO-8SO-8SOT-237.29x7.293.51mm12x12x4.5mm16mmD25mmH

120612.5mmD30mm

H

120612061206

30V,13.5mΩ,@4.5V

15.3nC30V,13.5mΩ,@4.5V

15.3nC

30V1µH,11A3.7mΩ1µH,11A,3.7mΩ5600µF10V2.35Arms

1µF,25V4700µF16V2.8Arms

0.1µF,25V2.2µF,25V12nF,25VParameters

Qty.111111112111

VendorNSCVishayVishayVishayPulsePulseSanyoTDKSanyoVishayTDKVishay

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LM2727/LM2737TABLE5.BillofMaterialsforCircuitofFigure5(Continued)

IDCc1Cc2RinRfadjRc1Rfb1Rfb2Rcs

PartNumberVJ1206A4R7KXXVJ1206A681KXXCRCW1206100JCRCW120992FCRCW12061473FCRCW12061492FCRCW120991FCRCW1206332J

TypeCapacitorCapacitorResistorResistorResistorResistorResistorResistor

Size12061206120612061206120612061206

Parameters4.7pF10%680pF10%10Ω5%49.9kΩ1%147kΩ1%14.9kΩ1%4.99kΩ1%3.3kΩ5%

Qty.11111111

VendorVishayVishayVishayVishayVishayVishayVishayVishay

TABLE6.BillofMaterialsforCircuitofFigure6

IDU1Q1/Q2D1LinL1Cin1Co1CbootCinCssCc1Cc2Cc3RinRfadjRc1Rc2Rfb1Rfb2Rcs

PartNumberLM2727Si4826DYBAT-54RLF7030T-1R0NRLF7030T-3R3M4R1C4532X5R1E156MC4532X5R1E156MVJ1206X104XXAC3216X7R1E225KVJ1206X393KXXVJ1206A220KXXVJ1206A681KXXVJ1206A681KXXCRCW1206100JCRCW12061742FCRCW12061072FCRCW120666R5FCRCW120991FCRCW12061002FCRCW1206152J

TypeSynchronousControllerAssymetricDualN-MOSFETSchottkyDiodeInductorInductorMLCCMLCCCapacitorCapacitorCapacitorCapacitorCapacitorCapacitorResistorResistorResistorResistorResistorResistorResistor

SizeTSSOP-14SO-8SOT-236.8x7.1x3.2mm6.8x7.1x3.2mm

181218121206120612061206120612061206120612061206120612061206

30V,24mΩ/8nCTop16.5mΩ/15nC

30V

1µH,6.4A,7.3mΩ3.3µH,4.1A,17.4mΩ15µF25V3.3Arms15µF25V3.3Arms

0.1µF,25V2.2µF,25V39nF,25V22pF10%680pF10%680pF10%10Ω5%17.4kΩ1%10.7kΩ1%66.5Ω1%4.99kΩ1%10kΩ1%1.5kΩ5%Parameters

Qty.11111111111111111111

VendorNSCVishayVishayTDKTDKSanyoSanyoTDKTDKVishayVishayVishayVishayVishayVishayVishayVishayVishayVishayVishay

TABLE7.BillofMaterialsfor3.3VCircuitofFigure6(IdenticaltoBOMfor1.8Vexceptasnotedbelow)

IDL1Cc1Cc2Cc3Rc1Rc2Rfb1Rfb2

PartNumberRLF7030T-4R7M3R4VJ1206A270KXXVJ1206X102KXXVJ1206A821KXXCRCW12061212FCRCW12054R9FCRCW12062211FCRCW12061002F

TypeInductorCapacitorCapacitorCapacitorResistorResistorResistorResistor

Size6.8x7.1x3.2mm

1206120612061206120612061206

Parameters4.7µH,3.4A,26mΩ

27pF10%1nF10%820pF10%12.1kΩ1%54.9Ω1%2.21kΩ1%10kΩ1%

Qty.11111111

VendorTDKVishayVishayVishayVishayVishayVishayVishay

TABLE8.BillofMaterialsforCircuitofFigure7

IDU1

PartNumberLM2727

TypeSynchronousController

SizeTSSOP-14

Parameters

Qty.1

VendorNSC

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LM2727/LM2737TABLE8.BillofMaterialsforCircuitofFigure7(Continued)

IDU2Q1/Q2D1LinL1Cin1CinxCo1Co2CoxCbootCinCssCc1Cc2Cc3RfadjRc1Rc2Rfb1Rfb2Rcs

PartNumberLM78L05Si4826DYBAT-54RLF7030T-1R0NSLF12565T-4R2N5R5

16MV680WGC3216X5R1C106M16MV680WGC3216X5R10J06MVJ1206X104XXAC3216X7R1E225KVJ1206X123KXXVJ1206A8R2KXXVJ1206X102KXXVJ1206X472KXXCRCW12063252FCRCW12065232FCRCW120662371FCRCW12062211FCRCW12061002FCRCW1206202J

TypeVoltageRegulatorAssymetricDualN-MOSFETSchottkyDiodeInductorInductorAl-EMLCCMLCCMLCCCapacitorCapacitorCapacitorCapacitorCapacitorCapacitorResistorResistorResistorResistorResistorResistor

SizeSO-8SO-8SOT-236.8x7.1x3.2mm12.5x12.5x6.5mmD:10mmL:12.5mm

121018121206120612061206120612061206120612061206120612061206

30V,24mΩ/8nCTop16.5mΩ/15nC

30V

1µH,6.4A,7.3mΩ4.2µH,5.5A,15mΩ680µF16V3.4Arms10µF16V3.4Arms15µF25V3.3Arms10µF6.3V2.7A0.1µF,25V2.2µF,25V12nF,25V8.2pF10%1nF10%4.7nF10%32.5kΩ1%52.3kΩ1%2.37Ω1%2.21kΩ1%10kΩ1%2kΩ5%

111111111111

Parameters

Qty.11111111

VendorNSCVishayVishayTDKTDKSanyoTDKSanyoTDKVishayTDKVishayVishayVishayVishayVishayVishayVishayVishayVishayVishay

TABLE9.BillofMaterialsforCircuitofFigure8

IDU1Q1D2L1D1Cin1CinxCo1,Co2CoxCbootCinCssCc1Cc2Cc3RfadjRc1Rc2Rfb1Rfb2Rcs

PartNumberLM2727Si44DYMBRS330T3SLF12565T-470M2R4

MBR052016MV680WGC3216X5R1C106M16MV680WGC3216X5R10J06MVJ1206X104XXAC3216X7R1E225KVJ1206X123KXXVJ1206A561KXXVJ1206X392KXXVJ1206X223KXXCRCW12062673FCRCW12066192FCRCW12067503FCRCW12061371FCRCW12061002FCRCW1206122F

TypeSynchronousControllerN-MOSFETSchottkyDiodeInductorSchottkyDiodeAl-EMLCCAl-EMLCCCapacitorCapacitorCapacitorCapacitorCapacitorCapacitorResistorResistorResistorResistorResistorResistor

SizeTSSOP-14SO-8SO-812.5x12.8x4.7mm

181212061206D:10mmL:12.5mm

1206120612061206120612061206120612061206120612061206

30V,15mΩ,11.5nC

30V,3A47µH,2.7A53mΩ

20V0.5A680µF,16V,1.54Arms10µF,16V,3.4Arms680µF16V26mΩ10µF,6.3V2.7A0.1µF,25V2.2µF,25V12nF,25V56pF10%3.9nF10%22nF10%267kΩ1%61.9kΩ1%750kΩ1%1.37kΩ1%10kΩ1%1.2kΩ5%Parameters

Qty.111111121111111111111

VendorNSCVishayONTDKONSanyoTDKSanyoTDKVishayTDKVishayVishayVishayVishayVishayVishayVishayVishayVishayVishay

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LM2727/LM2737N-ChannelFETSynchronousBuckRegulatorControllerforLowOutputVoltagesPhysicalDimensions

inches(millimeters)unlessotherwisenoted

TSSOP-14PinPackageNSPackageNumberMTC14

LIFESUPPORTPOLICY

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