LM2678-ADJ中文资料

LM2678SIMPLESWITCHER®HighEfficiency5AStep-DownVoltageRegulatorGeneralDescriptionTheLM2678seriesofregulatorsaremonolithicintegratedcircuitswhichprovidealloftheactivefunctionsforastep-down(buck)switchingregulatorcapableofdrivingupto5Aloadswithexcellentlineandloadregulationcharacteristics.Highefficiency(90%)isobtainedthroughtheuseofalowON-resistanceDMOSpowerswitch.Theseriesconsistsoffixedoutputvoltagesof3.3V,5Vand12Vandanadjustableoutputversion.TheSIMPLESWITCHERconceptprovidesforacompletedesignusingaminimumnumberofexternalcomponents.Ahighfixedfrequencyoscillator(260KHz)allowstheuseofphysicallysmallersizedcomponents.AfamilyofstandardinductorsforusewiththeLM2678areavailablefromseveralmanufacturerstogreatlysimplifythedesignprocess.TheLM2678seriesalsohasbuiltinthermalshutdown,currentlimitingandanON/OFFcontrolinputthatcanpowerdowntheregulatortoalow50µAquiescentcurrentstandbycondition.Theoutputvoltageisguaranteedtoa±2%toler-ance.Theclockfrequencyiscontrolledtowithina±11%tolerance.FeaturesnEfficiencyupto92%nSimpleandeasytodesignwith(usingoff-the-shelfexternalcomponents)n120mΩDMOSoutputswitchn3.3V,5Vand12Vfixedoutputandadjustable(1.2Vto37V)versionsn50µAstandbycurrentwhenswitchedOFFn±2%maximumoutputtoleranceoverfulllineandloadconditionsnWideinputvoltagerange:8Vto40Vn260KHzfixedfrequencyinternaloscillatorn−40to+125˚CoperatingjunctiontemperaturerangeApplicationsnSimpletodesign,highefficiency(90%)step-downswitchingregulatorsnEfficientsystempre-regulatorforlinearvoltageregulatorsnBatterychargersTypicalApplication10088603SIMPLESWITCHER®isaregisteredtrademarkofNationalSemiconductorCorporation.October2003LM2678SIMPLESWITCHERHighEfficiency5AStep-DownVoltageRegulator©2003NationalSemiconductorCorporationDS100886(Note1)IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.InputSupplyVoltage45VON/OFFPinVoltage−0.1Vto6VSwitchVoltagetoGround−1VtoVINBoostPinVoltageVSW+8VFeedbackPinVoltage−0.3Vto14VPowerDissipationInternallyLimitedESD(Note2)2kVStorageTemperatureRange−65˚Cto150˚CSolderingTemperatureWave4sec,260˚CInfrared10sec,240˚CVaporPhase75sec,219˚COperatingRatingsSupplyVoltage8Vto40VJunctionTemperatureRange(TJ)−40˚Cto125˚CElectricalCharacteristicsLimitsappearinginboldtypefaceapplyovertheentirejunctiontemperaturerangeofoperation,−40˚Cto125˚C.SpecificationsappearinginnormaltypeapplyforTA=TJ=25˚C.LM2678-3.3SymbolParameterConditionsTypicalMinMaxUnits(Note3)(Note4)(Note4)VOUTOutputVoltageVIN=8Vto40V,100mA≤IOUT≤5A3.33.234/3.2013.366/3.399VηEfficiencyVIN=12V,ILOAD=5A82%LM2678-5.0SymbolParameterConditionsTypicalMinMaxUnits(Note3)(Note4)(Note4)VOUTOutputVoltageVIN=8Vto40V,100mA≤IOUT≤5A5.04.900/4.8505.100/5.150VηEfficiencyVIN=12V,ILOAD=5A84%LM2678-12SymbolParameterConditionsTypicalMinMaxUnits(Note3)(Note4)(Note4)VOUTOutputVoltageVIN=15Vto40V,100mA≤IOUT≤5A1211.76/11.6412.24/12.36VηEfficiencyVIN=24V,ILOAD=5A92%LM2678-ADJSymbolParameterConditionsTypMinMaxUnits(Note3)(Note4)(Note4)VFBFeedbackVoltageVIN=8Vto40V,100mA≤IOUT≤5AVOUTProgrammedfor5V1.211.186/1.1741.234/1.246VηEfficiencyVIN=12V,ILOAD=5A84%LM2678−40˚Cto125˚C.Specifica-tionsappearinginnormaltypeapplyforTA=TJ=25˚C.UnlessotherwisespecifiedVIN=12Vforthe3.3V,5VandAdjustableversionsandVIN=24Vforthe12Vversion.SymbolParameterConditionsTypMinMaxUnitsDEVICEPARAMETERSIQQuiescentCurrentVFEEDBACK=8V4.26mAFor3.3V,5.0V,andADJVersionsVFEEDBACK=15VFor12VVersionsISTBYStandbyQuiescentCurrentON/OFFPin=0V50100/150µAICLCurrentLimit76.1/5.758.3/8.75AILOutputLeakageCurrentVIN=40V,ON/OFFPin=0VVSWITCH=0VVSWITCH=−1V1620015µAmARDS(ON)SwitchOn-ResistanceISWITCH=5A0.120.14/0.225ΩfOOscillatorFrequencyMeasuredatSwitchPin260225280kHzDDutyCycleMaximumDutyCycle91%MinimumDutyCycle0%IBIASFeedbackBiasCurrentVFEEDBACK=1.3VADJVersionOnly85nAVON/OFFON/OFFThresholdVoltage1.40.82.0VION/OFFON/OFFInputCurrentON/OFFInput=0V2045µAθJAThermalResistanceTPackage,JunctiontoAmbient65(Note5)θJATPackage,JunctiontoAmbient45(Note6)θJCTPackage,JunctiontoCase2θJASPackage,JunctiontoAmbient56˚C/W(Note7)θJASPackage,JunctiontoAmbien