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ACT4070.pdf

ACT4070.pdf

上传者: hdingguo 2012-04-02 评分 0 0 0 0 0 0 暂无简介 简介 举报

简介:本文档为《ACT4070pdf》,可适用于IT/计算机领域,主题内容包含InnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomAO符等。

InnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomAOutputCurrentUptoEfficiencyVtoVInputRangeµAShutdownSupplyCurrentkHzSwitchingFrequencyAdjustableOutputVoltageCyclebyCycleCurrentLimitProtectionThermalShutdownProtectionInternalSoftStartFunctionFrequencyFoldBackatShortCircuitStabilitywithWideRangeofCapacitors,IncludingLowESRCeramicCapacitorsSOPEP(ExposedPad)PackageTheACTisacurrentmodestepdownDCDCconverterthatgeneratesuptoAoutputcurrentatkHzswitchingfrequencyThedeviceutilizesActiveSemi’sproprietaryISOBCDprocessforoperationwithinputvoltageuptoVConsumingonlyμAinshutdownmode,theACTishighlyefficientwithpeakefficiencyatwheninoperationProtectionfeaturesincludecyclebycyclecurrentlimit,thermalshutdown,andfrequencyfoldbackatshortcircuitThedevicealsoincludesaninternalsoftstartfunctiontopreventovershootTheACTisavailableinSOPEPexposedpadpackageandrequiresveryfewexternaldevicesforoperationGENERALDESCRIPTIONTYPICALAPPLICATIONCIRCUITTFTLCDMonitorsorTelevisionsandHDTVPortableDVDPlayersCarPoweredorBatteryPoweredEquipmentSetTopBoxesTelecomPowerSuppliesDSLandCableModemsandRoutersFEATURESAPPLICATIONSACTRev,WideInputAStepDownConverterwwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTORDERINGINFORMATIONPARTNUMBERTEMPERATURERANGEPACKAGEPINSPACKINGACTYHCtoCSOPEPTUBEACTYHTCtoCSOPEPTAPEREELPINCONFIGURATIONPINDESCRIPTIONPINNUMBERPINNAMEPINDESCRIPTIONBSBootstrapThispinactsasthepositiverailforthehighsideswitch’sgatedriverConnectanFbetweenthispinandSWINInputSupplyBypassthispintoGwithalowESRcapacitorSeeInputCapacitorinApplicationInformationsectionSWSwitchOutputConnectthispintotheswitchingendoftheinductorGGroundFBFeedbackInputThevoltageatthispinisregulatedtoVConnecttotheresistordividerbetweenoutputandgroundtosetoutputvoltageCOMPCompensationPinSeeCompensationTechniqueinApplicationInformationsectionENEnableInputWhenhigherthanV,thispinturnstheIConWhenlowerthanV,thispinturnstheICoffOutputvoltageisdischargedwhentheICisoffThispinhasasmallinternalpullupcurrenttoahighlevelvoltagewhenpinisnotconnectedNCNotConnectedEPEPExposedPadshownasdashedboxTheexposedthermalpadshouldbeconnectedtoboardgroundplaneandpinThegroundplaneshouldincludealargeexposedcopperpadunderthepackageforthermaldissipation(seepackageoutline)Theleadsandexposedpadshouldbeflushwiththeboard,withoutoffsetfromtheboardsurfaceSOPEPwwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTABSOLUTEMAXIMUMRATINGSPARAMETERVALUEUNITINtoGtoVENtoGtoVINVBStoSWtoVFB,COMPtoGtoVContinuousSWCurrentInternallylimitedAJunctiontoAmbientThermalResistance(θJA)CWMaximumPowerDissipationWOperatingJunctionTemperaturetoCStorageTemperaturetoCLeadTemperature(Soldering,sec)CSWtoGtoVINVELECTRICALCHARACTERISTICS(VIN=V,TA=C,unlessotherwisespecified)PARAMETERSYMBOLTESTCONDITIONSMINTYPMAXUNITInputVoltageVINVOUT=V,ILOAD=AtoAVFeedbackVoltageVFBVHighSideSwitchOnResistanceRONHmΩLowSideSwitchOnResistanceRONLΩSWLeakageVEN=,VIN=V,VSW=VµACurrentLimitILIMACOMPtoCurrentLimitTransconductanceGCOMPΔILOADΔICOMPAVErrorAmplifierTransconductanceGEAΔICOMP=µAµAVErrorAmplifierDCGainAVEAVVSwitchingFrequencyfSWkHzShortCircuitSwitchingFrequencyVFB=VkHzMaximumDutyCycleDMAXVFB=V,PWMmodeMinimumDutyCycleVFB=V,PFMmodeEnableThresholdVoltageHysteresis=VVEnablePullUpCurrentPinpulleduptoVINwhenleftunconnectedµASupplyCurrentinShutdownVEN=µAICSupplyCurrentinOperationVEN=V,notswitchingmAThermalShutdownTemperatureHysteresis=CC:DonotexceedtheselimitstopreventdamagetothedeviceExposuretoabsolutemaximumratingconditionsforlongperiodsmayaffectdevicereliabilitywwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTFUNCTIONALBLOCKDIAGRAMFUNCTIONALDESCRIPTIONAsseenintheFunctionalBlockDiagram,theACTisacurrentmodepulsewidthmodulation(PWM)converterTheconverteroperatesasfollows:AswitchingcyclestartswhentherisingedgeoftheOscillatorclockoutputcausestheHighSidePowerSwitchtoturnonandtheLowSidePowerSwitchtoturnoffWiththeSWsideoftheinductornowconnectedtoIN,theinductorcurrentrampsuptostoreenergyintheitsmagneticfieldTheinductorcurrentlevelismeasuredbytheCurrentSenseAmplifierandaddedtotheOscillatorrampsignalIftheresultingsummationishigherthantheCOMPvoltage,theoutputofthePWMComparatorgoeshighWhenthishappensorwhenOscillatorclockoutputgoeslow,theHighSidePowerSwitchturnsoffandtheLowSidePowerSwitchturnsonAtthispoint,theSWsideoftheinductorswingstoadiodevoltagebelowground,causingtheinductorcurrenttodecreaseandmagneticenergytobetransferredtooutputThisstatecontinuesuntilthecyclestartsagainTheHighSidePowerSwitchisdrivenbylogicusingBSbootstrappinasthepositiverailThispinischargedtoVSWVwhentheLowSidePowerSwitchturnsonTheCOMPvoltageistheintegrationoftheerrorbetweenFBinputandtheinternalVreferenceIfFBislowerthanthereferencevoltage,COMPtendstogohighertoincreasecurrenttotheoutputCurrentlimithappenswhenCOMPreachesitsmaximumclampvalueofVTheOscillatornormallyswitchesatkHzHowever,ifFBvoltageislessthanV,thentheswitchingfrequencydecreasesuntilitreachesatypicalvalueofkHzatVFB=VShutdownControlTheACThasanenableinputENforturningtheIConoroffWhenENislessthanV,theICisinμAlowcurrentshutdownmodeandoutputisdischargedthroughtheLowSidePowerSwitchWhenENishigherthanV,theICisinnormaloperationmodeENisinternallypulledupwithaμAcurrentsourceandcanbeleftunconnectedforalwaysonoperationThermalShutdownTheACTautomaticallyturnsoffwhenitsjunctiontemperatureexceedsCandthenrestartsoncethetemperaturefallstoCwwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTOutputVoltageSettingFigureshowstheconnectionsforsettingtheoutputvoltageSelecttheproperratioofthetwofeedbackresistorsRFBandRFBbasedontheoutputvoltageTypically,useRFBkΩanddetermineRFBfromtheoutputvoltage:TheinductormaintainsacontinuouscurrenttotheoutputloadThisinductorcurrenthasaripplethatisdependentontheinductancevalue:higherinductancereducesthepeaktopeakripplecurrentThetradeoffforhighinductancevalueistheincreaseininductorcoresizeandseriesresistance,andthereductionincurrenthandlingcapabilityIngeneral,selectaninductancevalueLbasedonripplecurrentrequirement:VOUTVVVVVLμHμHμHμHμHVVRROBFBRIPPLEOUTMAXSWINOUTINOUTKIfVVVVLTheinputcapacitorneedstobecarefullyselectedtomaintainsufficientlylowrippleatthesupplyinputoftheconverterAlowESRcapacitorishighlyrecommendedSincelargecurrentflowsinandoutofthiscapacitorduringswitching,itsESRalsoaffectsefficiencyTheinputcapacitanceneedstobehigherthanµFThebestchoiceistheceramictypehowever,lowESRtantalumorelectrolytictypesmayalsobeusedprovidedthattheRMSripplecurrentratingishigherthanoftheoutputcurrentTheinputcapacitorshouldbeplacedclosetotheINandGpinsoftheIC,withshortesttracespossibleInthecaseoftantalumorelectrolytictypes,theycanbefurtherawayifasmallparallelµFceramiccapacitorisplacedrightnexttotheICTheoutputcapacitoralsoneedstohavelowESRtokeeplowoutputvoltagerippleTheoutputripplevoltageis:whereIOUTMAXisthemaximumoutputcurrent,KRIPPLEistheripplefactor,RESRistheESRresistanceoftheoutputcapacitor,fSWistheswitchingfrequency,Lintheinductorvalue,COUTistheoutputcapacitanceInthecaseofceramicoutputcapacitors,RESRisverysmallanddoesnotcontributetotherippleTherefore,alowercapacitancevaluecanbeusedforceramictypeInthecaseoftantalumorelectrolytictype,therippleisdominatedbyRESRmultipliedbytheripplecurrentInthatcase,theoutputcapacitorischosentohavesufficientlylowESRForceramicoutputtype,typicallychooseacapacitanceofaboutµFFortantalumorelectrolytictype,chooseacapacitorwithlessthanmΩESROUTSWINRIPPLERIPPLEOUTMAXRIPPLELCfVRKIVRectifierDiodeUseaSchottkydiodeastherectifiertoconductcurrentwhentheHighSidePowerSwitchisoffTheSchottkydiodemusthavecurrentratinghigherthanthemaximumoutputcurrentandthereversevoltageratinghigherthanthemaximuminputvoltageOutputCapacitorInductorSelectionTable:TypicalInductorValuesInputCapacitorAPPLICATIONSINFORMATIONwhereVINistheinputvoltage,VOUTistheoutputvoltage,fSWistheswitchingfrequency,IOUTMAXisthemaximumoutputcurrent,andKRIPPLEistheripplefactorTypically,chooseKRIPPLE=betweenandtocorrespondtothepeaktopeakripplecurrentbeingapercentageofthemaximumoutputcurrentWiththisinductorvalue(Table),thepeakinductorcurrentisIOUT(KRIPPLE)MakesurethatthispeakinductorcurrentislessthattheAcurrentlimitFinally,selecttheinductorcoresizesothatitdoesnotsaturateatA()()()Figure:OutputVoltageSettingwwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTStabilitycompensationThefeedbacksystemoftheICisstabilizedbythecomponentsatCOMPpin,asshowninFigureTheDCloopgainofthesystemisdeterminedbythefollowingequation:COMPVEAOUTVDCGAIVAThedominantpolePisduetoCCOMP:COMPVEAEAPCAGfCOMPCOMPZCRfAndfinally,thethirdpoleisduetoRCOMPandCCOMP(ifCCOMPisused):COMPCOMPPCRfFollowthefollowingstepstocompensatetheIC:STEPSetthecrossoverfrequencyatoftheswitchingfrequencyviaRCOMP:butlimitRCOMPtokΩmaximumOUTOUTOUTPCVIfThefirstzeroZisduetoRCOMPandCCOMP:ThesecondpolePistheoutputpole:STEPSetthezerofZatofthecrossoverfrequencyIfRCOMPislessthankΩ,theequationforCCOMPis:IfRCOMPislimitedtokΩ,thentheactualcrossoverfrequencyis(VOUTCOUT)Therefore:OUTOUTCOMPCVxCSTEPIftheoutputcapacitor’sESRishighenoughtocauseazeroatlowerthantimesthecrossoverfrequency,anadditionalcompensationcapacitorCCOMPisrequiredTheconditionforusingCCOMPis:AndthepropervalueforCCOMPis:COMPESROUTOUTCOMPRRCCThoughCCOMPisunnecessarywhentheoutputcapacitorhassufficientlylowESR,asmallvalueCCOMPsuchaspFmayimprovestabilityagainstPCBlayoutparasiticeffectsTableshowssomecalculatedresultsbasedonthecompensationmethodaboveTable:TypicalCompensationforDifferentOutputVoltagesandOutputCapacitorsVOUTCOUTRCOMPCCOMPCCOMPVμFCeramickΩnFpFVμFCeramickΩnFpFVμFCeramickΩnFpFVμFSPCAPkΩnFpFVμFSPCAPkΩnFpFVμFSPCAPkΩnFpFFigureshowsasampleACTapplicationcircuitgeneratingaVAoutput()()()()()()()OUTOUTCOMPEASWOUTOUTCOMPCVxVGGfCVR(Ω)()V,CxMinROUTOUTESROUT()(Ω)COMPCOMPRxC()(F)(F):CCOMPisneededforboardparasiticandhighESRoutputcapacitor:CCOMPisneededonlyforhighESRoutputcapacitorFigure:StabilityCompensationwwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTFigure:ACTVAOutputApplication:DisaV,ASchottkydiodewithlowforwardvoltage,anIRBQorSKequivalentCcanbeeitheraceramiccapacitor(PanasonicECJYBCM)orSPCAP(SpecialtyPolymer)AluminumElectrolyticCapacitorsuchasPanasonicEEFCDJXRTheSPCapisbasedonaluminumelectrolyticcapacitortechnology,butusesasolidpolymerelectrolyteandhasverystablecapacitancecharacteristicsinbothoperatingtemperatureandfrequencycomparedtoceramic,polymer,andlowESRtantalumcapacitorsICACTBSINENCOMPFBSWGVINENABLEVtoVCµFVC(CCOMP)nFR(RCOMP)kC(CCOMP)pFRkDVALµHACnFRkVOUTC(COUT)µFVceramicorµHSPCapVAwwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTTYPICALPERFORMANCECHARACTERISTICS(CircuitofFigure,unlessotherwisespecified)InputVoltage(V)ACTSwitchingFrequencyvsInputVoltageSwitchingFrequency(kHz)ACTOutputCurrent(A)SurfaceTemperaturevsOutputCurrentSurfaceTemperature(C)VOUT=VL=µHCIN=µFCOUT=µFVIN=VVIN=VVIN=VACTInputVoltage(V)ShutdownSupplyCurrent(µA)ShutdownSupplyCurrentvsInputVoltageEfficiency()OutputCurrent(A)ACTEfficiencyvsOutputCurrentVOUT=VL=µHCIN=µFCOUT=µFVIN=VVIN=VVIN=VVIN=VEfficiency()OutputCurrent(A)ACTEfficiencyvsOutputCurrentVOUT=VL=µHCIN=µFCOUT=µFVIN=VVIN=VVIN=VVIN=VTemperature(C)ACTFeedbackVoltage(V)FeedbackVoltagevsTemperaturewwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTTYPICALPERFORMANCECHARACTERISTICS(CircuitofFigure,unlessotherwisespecified)ACTVIN=VLoadTransientResponseVOUTmVdivAIOUTAµsdivACTVIN=VLoadTransientResponseAIOUTAVOUTmVdivµsdivACTVIN=VLoadTransientResponseVOUTmVdivAIOUTAµsdivwwwDataSheetUcomInnovativeProductsActiveSolutionsCopyrightActiveSemi,IncwwwactivesemicomACTSYMBOLDIMENSIONINMILLIMETERSDIMENSIONININCHESMINMAXMINMAXAAAbcDDEEEeTYPTYPLθActiveSemi,IncreservestherighttomodifythecircuitryorspecificationswithoutnoticeUsersshouldevaluateeachproducttomakesurethatitissuitablefortheirapplicationsActiveSemiproductsarenotintendedorauthorizedforuseascriticalcomponentsinlifesupportdevicesorsystemsActiveSemi,Incdoesnotassumeanyliabilityarisingoutoftheuseofanyproductorcircuitdescribedinthisdatasheet,nordoesitconveyanypatentlicenseActiveSemianditslogoaretrademarksofActiveSemi,IncFormoreinformationonthisandotherproducts,contactsalesactivesemicomorvisithttp:wwwactivesemicomForotherinquiries,pleasesendto:OakmeadParkway,Suite,Sunnyvale,California,USAPACKAGEOUTLINESOPEPPACKAGEOUTLINEANDDIMENSIONSDeDbwwwDataSheetUcom

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