电源芯片 LM2576.PDF

LM2576/LM2576HVSeriesSIMPLESWITCHER®3AStep-DownVoltageRegulatorGeneralDescriptionTheLM2576seriesofregulatorsaremonolithicintegratedcircuitsthatprovidealltheactivefunctionsforastep-down(buck)switchingregulator,capableofdriving3Aloadwithexcellentlineandloadregulation.Thesedevicesareavail-ableinfixedoutputvoltagesof3.3V,5V,12V,15V,andanadjustableoutputversion.Requiringaminimumnumberofexternalcomponents,theseregulatorsaresimpletouseandincludeinternalfrequencycompensationandafixed-frequencyoscillator.TheLM2576seriesoffersahigh-efficiencyreplacementforpopularthree-terminallinearregulators.Itsubstantiallyre-ducesthesizeoftheheatsink,andinsomecasesnoheatsinkisrequired.AstandardseriesofinductorsoptimizedforusewiththeLM2576areavailablefromseveraldifferentmanufacturers.Thisfeaturegreatlysimplifiesthedesignofswitch-modepowersupplies.Otherfeaturesincludeaguaranteed±4%toleranceonout-putvoltagewithinspecifiedinputvoltagesandoutputloadconditions,and±10%ontheoscillatorfrequency.Externalshutdownisincluded,featuring50μA(typical)standbycur-rent.Theoutputswitchincludescycle-by-cyclecurrentlimit-ing,aswellasthermalshutdownforfullprotectionunderfaultconditions.Featuresn3.3V,5V,12V,15V,andadjustableoutputversionsnAdjustableversionoutputvoltagerange,1.23Vto37V(57VforHVversion)±4%maxoverlineandloadconditionsnGuaranteed3AoutputcurrentnWideinputvoltagerange,40Vupto60VforHVversionnRequiresonly4externalcomponentsn52kHzfixedfrequencyinternaloscillatornTTLshutdowncapability,lowpowerstandbymodenHighefficiencynUsesreadilyavailablestandardinductorsnThermalshutdownandcurrentlimitprotectionnP+ProductEnhancementtestedApplicationsnSimplehigh-efficiencystep-down(buck)regulatornEfficientpre-regulatorforlinearregulatorsnOn-cardswitchingregulatorsnPositivetonegativeconverter(Buck-Boost)TypicalApplication(FixedOutputVoltageVersions)SIMPLESWITCHER®isaregisteredtrademarkofNationalSemiconductorCorporation.DS011476-1FIGURE1.June1999LM2576/LM2576HVSeriesSIMPLESWITCHER3AStep-DownVoltageRegulator©1999NationalSemiconductorCorporationDS011476−40˚C≤TA≤125˚CLM2576HVS-3.3LM2576HVS-5.0LM2576HVS-12LM2576HVS-15LM2576HVS-ADJTS5BTO-263LM2576S-3.3LM2576S-5.0LM2576S-12LM2576S-15LM2576S-ADJLM2576HVSX-3.3LM2576HVSX-5.0LM2576HVSX-12LM2576HVSX-15LM2576HVSX-ADJTS5BTape&ReelLM2576SX-3.3LM2576SX-5.0LM2576SX-12LM2576SX-15LM2576SX-ADJLM2576HVT-3.3LM2576HVT-5.0LM2576HVT-12LM2576HVT-15LM2576HVT-ADJT05ATO-220LM2576T-3.3LM2576T-5.0LM2576T-12LM2576T-15LM2576T-ADJLM2576HVT-3.3LM2576HVT-5.0LM2576HVT-12LM2576HVT-15LM2576HVT-ADJT05DFlowLB03FlowLB03FlowLB03FlowLB03FlowLB03LM2576T-3.3LM2576T-5.0LM2576T-12LM2576T-15LM2576T-ADJFlowLB03FlowLB03FlowLB03FlowLB03FlowLB03DS011476-23.3VR2=1.7k5V,R2=3.1k12V,R2=8.84k15V,R2=11.3kForADJ.VersionR1=Open,R2=0ΩPatentPending(Note1)IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.MaximumSupplyVoltageLM257645VLM2576HV63VON/OFFPinInputVoltage−0.3V≤V≤+VINOutputVoltagetoGround(SteadyState)−1VPowerDissipationInternallyLimitedStorageTemperatureRange−65˚Cto+150˚CMaximumJunctionTemperature150˚CMinimumESDRating(C=100pF,R=1.5kΩ)2kVLeadTemperature(Soldering,10Seconds)260˚COperatingRatingsTemperatureRangeLM2576/LM2576HV−40˚C≤TJ≤+125˚CSupplyVoltageLM257640VLM2576HV60VLM2576-3.3,LM2576HV-3.3ElectricalCharacteristicsSpecificationswithstandardtypefaceareforTJ=25˚C,andthosewithboldfacetypeapplyoverfullOperatingTemperatureRange.SymbolParameterConditionsLM2576-3.3Units(Limits)LM2576HV-3.3TypLimit(Note2)SYSTEMPARAMETERS(Note3)TestCircuitFigure2VOUTOutputVoltageVIN=12V,ILOAD=0.5A3.3VCircuitofFigure23.234V(Min)3.366V(Max)VOUTOutputVoltage6V≤VIN≤40V,0.5A≤ILOAD≤3A3.3VLM2576CircuitofFigure23.168/3.135V(Min)3.432/3.465V(Max)VOUTOutputVoltage6V≤VIN≤60V,0.5A≤ILOAD≤3A3.3VLM2576HVCircuitofFigure23.168/3.135V(Min)3.450/3.482V(Max)ηEfficiencyVIN=12V,ILOAD=3A75%LM2576-5.0,LM2576HV-5.0ElectricalCharacteristicsSpecificationswithstandardtypefaceareforTJ=25˚C,andthosewithFigure2boldfacetypeapplyoverfullOperatingTemperatureRange.SymbolParameterConditionsLM2576-5.0Units(Limits)LM2576HV-5.0TypLimit(Note2)SYSTEMPARAMETERS(Note3)TestCircuitFigure2VOUTOutputVoltageVIN=12V,ILOAD=0.5A5.0VCircuitofFigure24.900V(Min)5.100V(Max)VOUTOutputVoltage0.5A≤ILOAD≤3A,5.0VLM25768V≤VIN≤40V4.800/4.750V(Min)CircuitofFigure25.200/5.250V(Max)VOUTOutputVoltage0.5A≤ILOAD≤3A,5.0VLM2576HV8V≤VIN≤60V4.800/4.750V(Min)CircuitofFigure25.225/5.275V(Max)ηEfficiencyVIN=12V,ILOAD=3A77%=25˚C,andthosewithboldfacetypeapplyoverfullOperatingTemperatureRange.SymbolParameterConditionsLM2576-12Units(Limits)LM2576HV-12TypLimit(Note2)SYSTEMPARAMETERS(Note3)TestCircuitFigure2VOUTOutputVoltageVIN=25V,ILOAD=0.5A12VCircuitofFigure211.76V(Min)12.24V(Max)VOUTOutputVoltage0.5A≤ILOAD≤3A,12VLM257615V≤VIN