具有宽vin范围的低静态电流同步升压直流dc-控制器

具有宽VIN范围的低静态电流同步升压直流(DC)-DC控制查询样品TPS43060特 应用范58V最大输出电 用于PC的Thunderbolt端4.5V至38V（40V绝对最大值）VIN范 同步回应晶体管(MOSFET)而进行优化的7.5V栅极驱 TPS43061：针对低Qg而进行优化的5.5V栅极驱 动NexFET™ 5V，12V和24VDC总线电源系50kHz1MHz 说 TPS43060andTPS43061是低IQ电流模式同步升 ±0.8%反馈基准电 5µA关断电源电 600µA运行静态电 有PowerPad™的3mmx3mmQFN-16封装组合

小型16引脚四方扁平无引线(QFN)(3mmx3mm) 于驱动很多类型的MOSFET。TPS43061具有一个封装，此封装具有PowerPAD™ 5.5V栅极驱动电源并且其驱动强度针对低Qg-40°C至150°C的运行TJ范 SIMPLIFIEDNote1:DisrequiredforTPS43060,butoptionalforPleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsTexasInstrumentssemiconductorproductsanddierstheretoappearsattheendofthisdataCopyright©2012,TexasInstrumentsNexFET,PowerPADCopyright©2012,TexasInstrumentsPRODUCTIONDATAinformationiscurrentasofpublicationdate.ProductsconformtospecificationsperthetermsoftheInstrumentsstandardwarranty.Productionprocessingdoes EnglishDataSheet:necessarilyincludetestingofallThesedeviceshavelimitedbuilt-inESDprotection.TheleadsshouldbeshortedtogetherorthedevicecedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.DEVICETable1.OrderingInformationPART-40˚CtoQFN--40˚CtoQFN-Forthemostcurrentpackageandorderinginformation,seethePackageOptionAddendumattheendofthis,orseetheTIwebsiteatTheRTEpackageisavailableinlargeandsmallreelpackaging.AddanRsuffixtothedevicetype(TPS43061RTER)forthelargereel,orT(TPS43061RTET)forthesmallreel.(TOPVIEW)

PIN1ResistorTimingandExternalClock.AnexternalresistorfromthispintotheAGNDpinprogramstheswitchingfrequencybetween50kHzand1MHz.Drivingthepinwithanexternalclockbetween300kHzto1MHzwillsynchronizetheswitchingfrequencytotheexternalclock.2Soft-startprogrammingpin.AcapacitorbetweentheSSpinandAGNDpinsetssoft-start3Outputoftheinternaltransconductanceerroramplifier.ThefeedbackloopcompensationnetworkisconnectedfromthispintoAGND.4Erroramplifierinputandfeedbackpinforvoltageregulation.Connectthispintothecentertapofaresistordividertosettheoutputvoltage.5Inductorcurrentsensecomparatorinvertinginputpin.Thispinisnormallyconnectedtotheinductorsideofthecurrentsenseresistor.6Inductorcurrentsensecomparatornon-invertinginputpin.ThispinisnormallyconnectedtotheVINsideofthecurrentsenseresistor.7TheinputsupplypintotheIC.ConnectVINtoasupplyvoltagebetween4.5Vand38V.ItisacceptableforthevoltageontheVINpintobedifferentfromtheboostpowerstageinput,ISNS+andISNS-pins.8Lowsidegatedriveroutput.ConnectthispintothegateofthelowsideN-channelMOSFET.WhenVINbiasisremoved,aninternal200kΩresistorpullsLDRVtoPGND.9PowergroundoftheIC.Connectthispintothesourceofthelow-sideMOSFET.PGNDshouldbeconnectedtoAGNDviaasinglepointonprintedcircuitboard.PINFUNCTIONS(OutputofaninternalLDOandpowersupplyforinternalcontrolcircuitsandgatedrivers.VCCistypically7.5VfortheTPS43060and5.5VfortheTPS43061.ConnectalowESRceramiccapacitorfromthispintoPGND.The mendedcapacitancerangeisfrom0.47µFto10µF.Bootstrapcapacitornodeforhigh-sideMOSFETgatedriver.ConnectthebootstrapcapacitorfromthispintotheSWpin.FortheTPS43060,alsoconnectabootstrapdiodefromVCCtoBOOT.Switchingnodeoftheboostconverter.ConnectthispintothejunctionofthedrainofthelowsideMOSFET,thesourceofhighsidesynchronousMOSFETandtheinductor.Highsidegatedriveroutput.ConnectthispintothegateofthehighsidesynchronousrectifierMOSFET.WhenVINbiasisremoved,thispinisconnectedtoSWthroughaninternal200kΩresistor.Powergoodindicator.Thispinisanopen-drainoutput.A10kΩpull-upresistoris betweenPGOODandVCCoranexternallogicsupplypin.Enablepinwithinternalpull-upcurrentsource.FloatingthispinwillenabletheIC.Pullbelow1.2Vtoenterlowcurrentstandbymode.Pullbelow0.4Vtoentershutdownmode.TheENpincanbeusedtoimplementadjustableundervoltagelockout(UVLO)usingtworesistors.ogsignalgroundoftheIC.AGNDshouldbeconnectedtoPGNDatasinglepointonprintedcircuitThePowerPADshouldbeconnectedtoAGND.Ifpossible,usethermalviastoconnecttoaninternalgroundneforimprovedpowerdissipation.FUNCTIONALBLOCKISNS-

ABSOLUTEUMoveroperating-airtemperaturerange(unlessotherwiseInput:VIN,EN,-VDCVoltage:-VTransientVoltage(10nsmax):-VFB,RT/CLK,COMP,-VBOOT,HDRVVoltagewithRespecttoVBOOT,HDRVVoltagewithRespecttoSW8VVCC,PGOOD,-8VElectrostatic(HBM)QSS009-105(JESD22-2(CDM)QSS009-147(JESD22-VOperatingJunctionTemperature-StorageTemperature-THERMALoveroperating-airtemperaturerange(unlessotherwiseTHERMALMETRICJunction-to-ambientthermalJunction-to-case(top)thermalJunction-to-boardthermalJunction-to-topcharacterizationJunction-to-boardcharacterizationJunction-to-case(bottom)thermal(1)Formoreinformationabouttraditionalandnewthermalmetrics,seetheICPackageThermalMetricsapplicationreport,MENDEDOPERATINGoveroperating-airtemperaturerange(unlessotherwiseInputvoltageVOutputvoltageVENvoltage0VExternalswitchingfrequencylogicinput0VOperatingjunction-ELECTRICALVIN=4.5to38V,TJ=-40ºCto+150ºC,unlessotherwisenoted.TypicalvaluesareatTA=TESTSUPPLYANDInputvoltageVInputundervoltageVIN4VVINVUndervoltagelockoutOperatingquiescentcurrentintoDevicenon-switching,RT=115kΩ,VFB=2ShutdownVEN=5ENpinvoltagethresholdtoVENramVENpinvoltagethresholdtoenabletheVENramVENpinvoltagethresholdtodisabletheVENram1VENpinpull-upVEN=1ENpinhysteresisVEN=1.ENtostartswitchingCVCC=0.47VCCVIN=12-38V,IVCC=0µAVVIN=4.5V,IVCC=0VVIN=12-38V,IVCC=0µAVVIN=4.5V,IVCC=0VVCCpinumoutputVOLTAGEREFERENCEANDERRORFeedbackVoltageTJ=VTJ=-40°CtoErrorAmplifierinputbiasCOMPpinsinkVFB=VREF+250mV,VCOMP=1.5VCOMPpinsourceVFB=VREF-250mV,VCOMP=1.5VCOMPpinclampHighclamp,VFB=VLowclamp,VFB=1.5COMPpinDutycycle=1VErroramplifierm-ErroramplifieroutputErroramplifiercrossover2CURRENTumcurrentsenseAt0%DutyumcurrentsenseAtMaxDutyReversecurrentsenseSense+pinSense-pinSwitchingOperatingfrequencyrangeusingresistortimingRT=115RT=75RT/CLKpinVELECTRICALCHARACTERISTICSELECTRICALCHARACTERISTICS)VIN=4.5to38V,TJ=-40ºCto+150ºC,unlessotherwisenoted.TypicalvaluesareatTA=TESTtCLK-MinimuminputclockpulsePLL=500vCLK-RT/CLKhigh2VRT/CLKlowVPLLfrequencysyncPLLlockinLastRT/CLKfallingedgetoreturntoresistortimingmodeifCLKisnotPOWERSWITCHLDRVpull-upVIN=12V-402ΩVIN=4.53VIN=12V-40ΩVIN=4.53LDRVpull-downVIN=12V-40ΩVIN=4.52VIN=12V-40ΩVIN=4.52HDRVpull-upVIN=12V-402ΩVIN=4.5VIN=12V-405ΩVIN=4.5HDRVpull-downVIN=12V-40ΩVIN=4.5VIN=12V-403ΩVIN=4.5Highsidegaterisetime,10%toCLOAD=2.2nF,VIN=12V-40Highsidegatefalltime,90%toCLOAD=2.2nF,VIN=12V-40Lowsidegaterisetime,10%toCLOAD=2.2nF,VIN=12V-40Lowsidegatefalltime,90%toCLOAD=2.2nF,VIN=12V-40BOOTdiodeforwardvoltageIF=10mA,TA=VBOOTpinleakageVr=60LDRVminimumonpulsefSW=500LDRVminimumoffpulsefSW=500TimedelaybetweenLDRVfall(50%)toHDRVrise(50%),CLOAD=open,fSW=500VIN=VIN=CLOAD=open,fSW=500VIN=VIN=TimedelaybetweenHDRVfall(50%)toLDRVrise(50%),CLOAD=open,fSW=500VIN=VIN=CLOAD=open,fSW=500VIN=VIN=TESTPOWERGOOD,SSANDPGOODlowVFBwithrespecttoFeedbackVoltageReference,VFBfallingPGOODlowVFBwithrespecttoFeedbackVoltagePGOODhighVFBwithrespecttoFeedbackVoltageReference,VFBrisingPGOODhighVFBwithrespecttoFeedbackVoltagePGOODsinkVPGOOD=0.44PGOODpinleakageVPGOOD=7MinimumVINforvalidVSoft-startbiasVSS=05Soft-startdischargeΩOVPVFBwithrespecttoFeedbackVoltageReference,VFBrisingOVPVFBwithrespecttoFeedbackVoltageTHERMALThermalshutdownsetThermalshutdownTYPICALVIN=12V,fSW=500kHz,TA=25ºC(unlessotherwiseInputVoltage(ShutdownInputVoltage(ShutdownCurrentFigure1.InputStartandStopVoltagevs Figure2.ShutdownSupplyCurrentvsNon-SwitchingSupplyCurrentFrequencyNon-SwitchingSupplyCurrentFrequencyVoltageReferenceCOMPVoltageFigure3.Non-SwitchingSupplyCurrentvsVoltageReferenceCOMPVoltageFigure5.FeedbackVoltageReferencevs Figure6.COMPClampVoltagevsTYPICALCHARACTERISTICSTYPICALCHARACTERISTICSVIN=12V,fSW=500kHz,TA=25ºC(unlessotherwise)EnableVoltageENPull-upCurrentENHysteresisCurrentFigureEnableVoltageENPull-upCurrentENHysteresisCurrentFigure9.EnableThresholdvs Figure10.ErrorAmplifierTransconductanceSSChargeSSChargeCurrentNormalizedFigure11.SSChargeCurrentvs Figure12.GateDriverOutputvs0%DutyMaxDutyVIN=12fsw=500OVPThresholdMaxCurrentThresholdFigure13.OVPThresholdvs Figure14.OVPThresholdMaxCurrentThresholdReverseCurrentSenseReverseCurrentSenseThresholdVCCVoltageVIN=12IVCC=0Figure15.ReverseCurrentSenseThresholdvs Figure16.VCCVoltagevsTemperatureDETAILEDTheTPS43060andTPS43061arehigh-performancewideinputrangesynchronousboostcontrollersthataccepta4.5Vto38V(40Vabsmax)inputandsupportoutputvoltagesupto58V.ThedeviceshavegatedriversforboththelowsideN-channelMOSFETandthehighsidesynchronousrectifierN-channelMOSFET.Voltageregulationisachievedemployingconstantfrequencycurrentmodepulsewidthmodulation()control.Theswitchingfrequencyisseteitherbyanexternaltimingresistororbysynchronizingtoanexternalclocksignal.Theswitchingfrequencyisprogrblefrom50kHzto1MHzintheresistorprogrammedmodeorcanbesynchronizedtoanexternalclockbetween300kHzto1MHz.ThecontrolcircuitryturnsonthelowsideMOSFETatthebeginningofeachoscillatorclockcycle,astheerroramplifiercomparestheoutputvoltagefeedbacksignalattheFBpintotheinternal1.22Vreferencevoltage.ThelowsideMOSFETisturned-offwhentheinductorcurrentreachesathresholdlevelsetbytheerroramplifieroutput.AfterthelowsideMOSFETisturnedoff,thehighsidesynchronousMOSFETisturnedonuntilthebeginningofthenextoscillatorclockcycleoruntiltheinductorcurrentreachesthereversecurrentsensethreshold.TheinputvoltageisappliedacrosstheinductorandstorestheenergyasinductorcurrentrampsupduringtheportionoftheswitchingcyclewhenthelowsideMOSFETison.Meanwhiletheoutputcapacitorsloadcurrent.WhenthelowsideMOSFETisturnedoffbythecontroller,theinductortransfersstoredenergyviathesynchronousMOSFETtoreplenishtheoutputcapacitorandsupplytheloadcurrent.Thisoperationrepeatseveryswitchingcycle.Thedevicesfeatureinternalslopecompensationtoavoidsub-harmonicoscillationthatisintrinsictopeakcurrentmodecontrolatdutycycleshigherthan50%.Theyalsofeatureadjustablesoft-starttime,optionallosslessinductorDCRcurrentsensing,anoutputpowergoodindicator,cycle-by-cyclecurrentlimitandover-temperatureSWITCHINGTheswitchfrequencyissetbyaresistor(RT)connectedtotheRT/CLKpinoftheTPS43060andTPS43061.TherelationshipbetweenthetimingRTandfrequencyisshownintheFigure17.TheresistorvaluerequiredforadesiredfrequencycanbecalculatedusingEquation1.TR(k) T

VCCVCCVoltage0 (k)Figure17.FrequencyvsRT

ThedeviceswitchingfrequencycanbesynchronizedtoanexternalclockthatisappliedtotheRT/CLKpin.Theexternalclockshouldbeintherangeof300kHzto1MHz.Therequiredlogiclevelsoftheexternalclockareshowninthespecificationtable.Thepulsewidthoftheexternalclockshouldbegreaterthan20nstoensurepropersynchronization.Aresistorbetween57.5kΩand1150kΩmustalwaysbeconnectedfromtheRT/CLKpintogroundwhentheconverterissynchronizedtoanexternalclock.Donotleavethispinopen.LOWDROPOUTTheTPS43060andTPS43061containalowdropoutregulatorsthatprovidesbiassupplyforthecontrollerandthegatedriver.TheoutputoftheLDOofTPS43060andTPS43061areregulatedto7.5Vand5.5V,respectively.WhentheinputvoltageisbelowtheVCCregulationleveltheVCCoutputtracksVINwithasmalldropoutvoltage.TheoutputcurrentoftheVCCregulatorshouldnotexceed50mA.ThevalueoftheVCCcapacitancedependsonthetotalsystemdesign,anditsstartupcharacteristics. mendedrangeofvaluesfortheVCCcapacitoris0.47µFto10INPUTUNDERVOLTAGEAnundervoltagedetectioncircuitpreventsmis-operationofthedeviceatinputvoltagesbelow3.9V(typical).WhentheinputvoltageisbelowtheVINUVthreshold,theinternal controlcircuitryandgatedriversareturnedoff.Thethresholdissetbelowminimumoperatingvoltageof4.5VtoensurethatatransientVINdipwillnotcausethedevicetoreset.ForinputvoltagesbetweentheUVthresholdand4.5V,thedeviceattemptstooperate,buttheelectricalspecificationsarenotensured.TheENpincanbeusedtoachieveadjustableUVLOifthedesiredstart-upthresholdishigherthan3.9V.Detailsareprovidedinthefollowingsection.ENABLEANDADJUSTABLEUNDERVOLTAGELOCKOUTTheENpinvoltagemustbegreaterthan1.21V(typical)toenableTPS43060andTPS43061.ThedeviceentersashutdownmodewhentheENvoltageislessthan0.4V.Inshutdownmode,theinputsupplycurrentforthedeviceislessthan5µA.TheENpinhasaninternal1.8μApull-upcurrentsourcethatprovidesthedefaultenabledconditionwhentheENpinfloats.WhentheENpinvoltageishigherthantheshutdownthresholdbutlessV,thedevicesareinstandbyAdjustableinputUVLOcanbe plishedusingtheENpin.AsshowninFigure18,aresistordividerfromtheVINpintoAGNDsetstheUVLOlevel.OnceENpinvoltagecrossesthe1.21V(typical)thresholdvoltageanadditional3.2μAhysteresiscurrentissourcedoutoftheENpin.WhenENpinvoltagefallsbelow1.14V(typical),thehysteresiscurrentisremoved.TheadditionofhysteresiscurrentattheENthresholdfacilitatesadjustableinputvoltagehysteresis.RUVLO_HandRUVLO_LarecalculatedusingEquation2andEquation3respectively.1Figure18.AdjustableUVLOusingEN RUVLO_H

EN_VVV

IEN_pup

EN_DISIEN_RUVLO_L

EN_ONREN_HVEN_

EN_ EN_ EN_ EN_ EN_ VSTARTisthedesiredturn-onvoltageattheVINVSTOPisthedesiredturn-offvoltageattheVINVEN_ONisENpinvoltagethresholdtoenablethedevice,1.21VVEN_DISisENpinvoltagethresholdtodisablethedevice,1.14VIEN_hysisthehysteresiscurrentinsidethedevice,3.2μAIEN_pupistheinternalpull-upcurrentatENpin,1.8μAVOLTAGEREFERENCEANDSETTINGOUTPUTAninternalvoltagereferenceprovidesaprecise1.22Vvoltagereferenceattheerroramplifiernon-invertinginput.Tosettheoutputvoltage,selecttheFBpinresistorRSHandRSLaccordingtoEquation4. RVOUT1.22VSHR MINIMUMON-TIMEANDPULSETheTPS43060andTPS43061alsofeatureaminimumon-timeof100nsforthelow-sidegatedriver.Thisminimumon-timedeterminestheminimumdutycycleoftheforanysetswitchingfrequency.Whenthevoltageregulationlooprequiresaminimumon-timepulsewidthlessthan100ns,thecontrollerenterspulse-skipmode.Inthismode,thedevicesholdthepowerswitchoffformultipleswitchingcyclestopreventtheoutputvoltagefromrisingabovethedesiredregulatedvoltage.ThisoperationtypicallyoccursinlightloadconditionswhentheDC-DCconverteroperatesindiscontinuousconductionmode.PulseskipincreasestheoutputrippleasshowninFigureZERO-CROSS-DETECTIONandDUTYD fallsbelowthereversecurrentsensethreshold(3.8mVtypical),thentheconverterrunsindiscontinuousconductionmode(DCM).Thedutycycleisdependentonthemodeinwhichtheconverterisoperating.ThedutycycleinDCMvarieswidelywithchangesoftheload.InCCM,wheretheinductormaintainsaminimumdccurrent,theD WhentheconverteroperatesinDCM,thedutycycleisafunctionoftheload,inputandoutputvoltages,inductanceandswitchingfrequencyinEquation6.D2VOUTIOUTLVIN

Equation5andEquation6provideanestimationofthedutycycle.AmoreaccuratedutycyclecanbecalculatedbyincludingthevoltagedropsoftheexternalMOSFETs,senseresistorandDCRoftheinductor.MINIMUMOFF-TIMEandUMDUTYThelowsidedriverLDRVofTPS43060andTPS43061hasaminimumoff-timeof250nsor5%oftheswitchingcycleperiodwhicheverislonger.Figure19showsumdutycyclevs.SwitchingFrequency.Theumdutycyclelimitstheumachievablestep-upratioinaBoostconverter.WhentheconverteroperatesinCCM,thestep-upratiooftheboostconvertercanbecalculatedusingEquation7.

1 Forinstance,iftheumdutycycleis90%,theachievableumoutputvoltagetoinputvoltageratioislimitedto:OUT

1 MaxDutyCycleFigure19.umDutyCycleMaxDutyCycleTheTPS43060andTPS43061haveabuilt-insoft-startcircuitwhichsignificantlyreducesthestart-upcurrenteandoutputvoltageovershoot.WhentheICisenabled,aninternalbiascurrentsource(5µAtypical)chargesthecapacitor(CSS)ontheSSpin.WhentheSSpinvoltageislessthantheinternal1.22Vreference,thedeviceregulatestheFBpinvoltagetotheSSpinvoltageratherthantheinternal1.22Vreferencevoltage.OncetheSSpinvoltageexceedsthereferencevoltagethedeviceregulatestheFBpinvoltageto1.22V.Thesoft-starttimeoftheoutputvoltagecanbecalculatedusingEquation9.tssCss POWERTheTPS43060andTPS43061PGOODpinindicateswhentheoutputvoltageiswithinpre-determinedlimitsofthedesiredregulatedoutputvoltagebymonitoringtheFBpinvoltage.ThePGOODpinisdrivenbytheopen-drainsignalofaninternalMOSFET.Whentheoutputvoltageofthepowerconverterisnotwithin±10%oftheoutputvoltagesetpoint,thePGOODMOSFETturnsonandpullsthePGOODpinlow.Otherwise,thePGOODMOSFETstaysoffandthePGOODpincanbepulledupbyanexternalresistortoavoltagesupplyupto8V.OVERVOLTAGETheTPS43060andTPS43061integrateanovervoltageprotection(OVP)circuitthatturnsoffthelowsideMOSFETwhentheoutputvoltagereachestheOVPthresholdwhichisinternallyfixedto107%oftheoutputvoltagesetpoint.ThelowsideMOSFETresumesnormalcontrolwhentheoutputvoltagedropsbelow105%oftheoutputvoltagesetpoint.TheOVPcircuitprotectsthepowerMOSFETsandminimizestheoutputvoltageovershootduringtransientsorfaultconditions.OVERCURRENTPROTECTIONANDCURRENTSENSERESISTORTheTPS43060andTPS43061providecycle-by-cyclecurrentlimitprotectionthatturnsoffthelowsideMOSFETwhentheinductorcurrentreachesthecurrentlimitthreshold.Thecycle-by-cyclecurrentlimitcircuitryisresetatthebeginningofthenextswitchingcycle.Duringanovercurrentevent,theoutputvoltagebeginstodroopasafunctionoftheloadontheoutput.Aslopecompensationrampisaddedtothecurrentsenseramptopreventsub-harmonicoscillationsathighdutycycle.Theslopecompensationreducestheovercurrentlimitthreshold(umcurrentsensethreshold)withincreasingdutycycleasdetailedinFigure20.Figure20.OverCurrentLimitThresholdwith umcurrentsensethresholdVCSmaxsetstheumpeakinductorcurrentwhichisthesumofumaverageinductor(input)currentIave_maxandhalfthepeak-to-peakinductorrippleΔIL.Thesensevalueshouldbechosenbasedonthedesireduminputcurrentandtheripplecurrent,andcanbecalculatedusingEquation10. VCS 2Iave_max 2GATETheTPS43060andTPS43061containpowerfulhigh-sideandlow-sidegatedriversdbytheVCCbiasregulator.ThenominalVCCvoltageoftheTPS43060andTPS43061is7.5Vand5.5Vrespectively.TheTPS43061gatedriversoperatefroma5.5VVCCsupply,withdrivestrengthoptimizedforlowQgNexFETs™.Italsofeaturesanintegratedbootstrapdiodeforthehighsidegatedrivertoreducetheexternalpartcount.TheTPS43060gatedriversoperatefroma7.5VVCCsupply,whichissuitabletodriveawiderangeofstandardMOSFETs.TheTPS43060requiresanexternalbootstrapdiodefromVCCtoBOOTtochargethebootstrapcapacitor.Italsorequiresa2ΩresistorconnectedinserieswiththeVCCpintolimitthepeakcurrentdrawnthroughtheinternalcircuitrywhentheexternalbootstrapdiodeisconducting.SeetheELECTRICALCHARACTERISTICStablefortypicalriseandfalltimesandtheoutputofthegatedrivers.TheLDRVandHDRVoutputsarecontrolledwithanadaptivedead-timecontrolthatensuresthatboththeoutputsareneverhighatthesametime.Thisminimizesanycrossconductionandprotectsthepowerconverter.Thetypicaldead-timefromLDRVfalltoHDRVriseis65ns.LAYOUTAswithallswitchingpowers,especiallythosewithhighfrequencyandhighswitchcurrent,printedcircuitboard(PCB)layoutisanimportantdesignstep.Iflayoutisnotcarefullydesigned,theregulatorcouldsufferfrominstabilityaswellasnoiseproblems.Toizeefficiency,switchriseandfalltimesaremadeasshortaspossible.Topreventradiationandhighfrequencyresonanceproblems,properlayoutofthehighfrequencyswitchingpathisessential.MinimizethelengthandareaofalltracesconnectedtotheSWpinandalwaysuseagroundneundertheswitchingregulatortominimizeinter-necoupling.ThehighcurrentpathincludingthelowsideMOSFET,highsideMOSFET,andoutputcapacitor,experiencenanosecondriseandfalltimesandshouldbekeptasshortaspossible.TheinputcapacitormustbelocatedclosetotheVINpinandtheAGNDpintoreducetheinputsupplyrippletothecontroller.THERMALAninternalthermalshutdownturnsofftheTPS43060andTPS43061whenthejunctiontemperatureexceedsthethermalshutdownthreshold(165°Ctypical).ThedevicewillrestartwhenthejunctiontemperaturedropsbyTHERMALTheumICjunctiontemperatureshouldberestrictedto150°Cundernormaloperatingconditions.ThisrestrictionlimitsthepowerdissipationoftheTPS43060andTPS43061.ThedevicesarepackagedinathermallyenhancedQFNpackagewhichincludesaPowerPAD™thatimprovesthethermalcapabilities.ThethermaloftheQFNpackageinanyapplicationgreatlydependsonthePCBlayoutandthePowerPADconnection.ThePowerPADmustbesolderedtotheoggroundonthePCB.UsethermalviasunderneaththePowerPADtoachievegoodthermalperformance.DESIGNGUIDE–TPS43061STEP-BY-STEPDESIGNThefollowingsectionprovidesastep-by-stepdesignguideofahigh-frequency,high-power-densitysynchronousboostconverterwiththeTPS43061controllercombinedwithaNexFET™powerblock.ThisdesignprocedureisalsoapplicabletotheTPS43060.Afewparametersmustbeknowninordertostartthedesignprocess.Theserequirementsaretypicallydeterminedatthesystemlevel.Forthisexample,wewillstartwiththefollowingknownTable2.KeyParametersoftheBoostConverterInputvoltage6Vto12.6V,9VOutputvoltage15umoutputcurrent2Transientresponseto0.5Ato1.5Aloadstep4%ofVOUT=0.6Outputvoltageripple0.5%ofVOUT=0.075Startinputvoltage5.34Startinputvoltage4.3Figure21.TheSchematicofSynchronousBoostConverterusingSELECTINGTHESWITCHINGThefirststepistodeterminetheswitchingfrequencyofthepowerconverter.Therearetradeoffstoconsiderwhenselectingahigherorlowerswitchingfrequency.Typically,thedesignerusesthehighestswitchingfrequencypossiblesincethisresultsinthesmallestsolutionsize.Ahigherswitchingfrequencyallowsforlowervalueinductorsandsmalleroutputcapacitorscomparedtoapowerconverterthatswitchesatalowerfrequency.Alowerswitchingfrequencywillproducealargersolutionsizebuttypicallyhasabetterefficiency.Settingthefrequencyfortheminimumtolerableefficiencywillproducetheoptimumsolutionsizefortheapplication.Theswitchingfrequencycanalsobelimitedbytheminimumon-timeandoff-timeofthecontrollerbasedontheinputvoltageandtheoutputvoltageoftheapplication.Todeterminetheumallowableswitchingfrequency,firstestimatethecontinuousconductionmode(CCM)dutycycleusingEquation11withtheminimumanduminputvoltages.Equation12andEquation13shouldthenbeusedtocalculatetheupperlimitofswitchingfrequencyfortheregulator.Choosethelowervalueresultfromthesetwoequations.Switchingfrequencieshigherthanthecalculatedvalueswillresultineitherpulseskipiftheminimumon-timerestrictsthedutycycleorinsufficientboostoutputvoltageifthedutycycleislimitedbytheminimumoff-time.DVOUTD fSWontimetonminD fSWofftimetoffmin

Thetypicalminimumon-timeandoff-timeofthedeviceare100nsand250nsrespectively.Forthisdesign,thedutycycleisestimatedat20%and60%withtheuminputvoltageandminimuminputvoltagerespectively.Whenoperatingatswitchingfrequencieslessthan200kHztheminimumofftimestartstoincreaseandisequalto5%theswitchingperiod.Theestimatedallowed umswitchingfrequencybasedonEquation12andEquation13is2MHz.Whenoperatingneartheestimated umdutycyclemoreaccurateestimationsofthedutycycleshouldbemadebyincludingthevoltagedropsoftheexternalMOSFETs,senseresistorandDCRoftheinductor.Aswitchingfrequencyof750kHzischosenasacompromisebetweenefficiencyandsmallsolutionsize.TodeterminethetimingforagivenswitchingfrequencyuseeitherEquation14orthecurveinFigure17.TheswitchingfrequencyissetbyresistorR5showninFigure21.For750kHzoperation,thecloseststandardvalueresistoris76.8kΩ.R(k) TfSW INDUCTORTheselectionoftheinductoraffectsthesteady-stateoperationaswellastransientbehaviorandloopstability.Thesefactorsmakeitanimportantcomponentinaswitchingpowersupplydesign.Thethreemostimportantinductorspecificationstoconsiderareinductorvalue,DC(DCR),andsaturationcurrentrating.LettheparameterKINDrepresenttheratioofinductorpeak-peakripplecurrenttotheaverageinductorcurrent.Inaboosttopologytheaverageinductorcurrentisequaltotheinputcurrent.Thecurrentdeliveredtotheoutputistheinputcurrentmodulatedatthedutycycleofthe.Theinductorripplecurrentcontributestotheoutputcurrentripplethatmustbefilteredbytheoutputcapacitor.Therefore,choosinghighinductorripplecurrentsimpactstheselectionoftheoutputcapacitor.ThevalueofKINDinthedesignusinglowESRoutputcapacitors,suchasceramics,canberelativelyhigherthanthatinthedesignusinghigherESRoutputcapacitors.HighervaluesofKINDleadtodiscontinuousmode(DCM)operationatmoderatetolightloads.Tocalculatetheminimumvalueoftheoutputinductor,useEquation16orEquation17.Inaboosttopologyumcurrentrippleoccursat50%dutycycle.UseEquation16ifthedesignwilloperatewith50%Forthisdesignexample,Equation15producestheestimateduminputcurrent(IIN)of5A.Inrealitythiswillbehigherbecausethesimplifiedequationsdonotincludetheefficiencylossesofthepowersupply.UsingKIND0.3withEquation16,theminimuminductorvalueiscalculatedtobe3.33µH.Theneareststandardvalueof3.3µHischosen.ItisimportantthattheRMScurrentandsaturationcurrentratingsoftheinductornotbeexceeded.TheRMSandpeakinductorcurrentcanbefoundfromEquation18andEquation19,respectively.ThecalculatedRMSinductorcurrentis5.0Aandthepeakinductorcurrentis5.73A.ThechoseninductorisaVishayIHLP2525CZER3R3M1whichhasanRMScurrentratingof6A,asaturationcurrentratingof10Aand30mΩ 5 1D 1 L IINL IIN

4D

5A 4 ILrms

5

Ipeak VINminDmax 6V 1D 2Lf 1 23.3H Selectinghigherripplecurrentswillincreasetheoutputvoltage