W7812稳压管

MDC_78xxSRSeries.B03Page1of678xxSRSeries3.3V/5V/12VOutputsHigh-EfficiencySwitchingRegulatorswithLM78xxPinoutsForfulldetailsgoto:[e-mail],tel:[phone]MurataPowerSolutions’7805SR-C(5Voutput),7812SR-C(12Voutput)and7803SR-C(3.3Voutput)step-downswitchingregulatorsaremoderndrop-inreplacementsforolder,inefficient,LM7805andLM7812linearregulators.The78XXSR'sarepin-andsize-compat-iblewithindustry-standardTO-220SIPpackages.A260kHzswitchingfrequencyprovidesforefficienciesashighas95%.Full-load(upto0.5A)operationfrom9V,12V,24V,or36Vsuppliesatambienttemperaturesupto+70°Crequiresnoheatsinks,notemperaturederating,noforced-aircooling,andnoexternalcapacitors.78SRswitchingregulatorsprovidemanysignificantimprovementsovertheirlinearcounterparts:lowerquiescentcurrent(3mAvs.5mA),higherinputvoltage(40Vvs.32V),andbetteroutputaccuracy(±1.5%vs.±5%).Allthesefeaturescombinetomake78SRregulatorsidealforneworexistingLM7805&LM7812applicationsrequiringfull-loadoperationatelevatedvoltages.TECHNICALNOTES1.Input/Output(I/O)Filtering:Asshowninthenoiseandripplegraphs,78SRswitchingregulatorsexhibitexcellentlow-noiseperformancewithnoexternalI/Ocapacitors.However,ifadditionalnoisereductionisrequired,besuretouselow-ESRcapacitorsthatareratedforcontinuousoperation(withanadditional20%safetymargin)atthehighestsystemvoltagesandtemperatures.Addingexternaloutputcapacitorswillalsoimprovetheunit’sload-transientresponse.Applicationsinwhich78SRregulatorsarelocatedmorethan24inches(61cm)fromtheinputpowersupplyshouldincludeanexternal47uF/50V(orgreater)aluminumelectrolyticcapacitor,connectedascloseaspossibletotheregulator’s+VinandGNDterminals(pins1and2).Anexternalinputcapacitorisparticularlyimportantiftheinputvoltageisappliedtotheregulatorviaamechanicalswitchorrelay.Contactbounceatturn-oncanproducelargeinductivecurrent-spikes,andthesecurrentspikescangeneratedamagingvoltagetransientsattheregulator’sinputterminals.2.InputFusing:78SRswitchingregulatorsarenotinternallyfused.Iffusingtheirinputand/oroutputterminalsisrequired,usethedatashownintheEfficiencyCurvesasaguidetoselectinganappropriateslow-blowfuse.3.Input-OutputIsolation:78SRregulators’internalinputandoutputcircuitsshareacommonconnection(GND,pin2);thereisnoelectricalisolationbetweentheINPUT(pin1)andOUTPUT(pin3)terminals.4.OvervoltageProtection:78SRswitchingregulatorsdonotprovideinputoroutputovervoltageprotection.Intheextremelyraresituationinwhichacatastrophicfailureoccurs,theoutputvoltagemayrisetoexcessivelyhighlevels.Ifyourloadmustbeprotectedagainstallpossibleovervoltagesituations,externalvoltage-limitingcircuitrymustbeprovided.5.Operationat40Vdc:Operatingwithinputsupto40Vdcispermissibleif,forinputsbetween36and40Vdc,themaximumloadcurrentisreducedto0.35Afor7805SR-Cand7803SR-C,andto0.3Afor7812SR-C.Undernocircumstancesshouldtheinputvoltagebeallowedtoexceed45Vdc.MPSPartNo.OutputOutputInputVoltageCurrentVoltageStandardPinPackage7803SR-C+3.3Vdc0.5A+7.5-36Vdc7805SR-C+5.0Vdc0.5A+7.5-36Vdc7812SR-C+12.0Vdc0.4A+15-36VdcHorizontalPinPackage7803SRH-C+3.3Vdc0.5A+7.5-36Vdc7805SRH-C+5.0Vdc0.5A+7.5-36Vdc7812SRH-C+12.0Vdc0.4A+15-36VdcOrderingInformationFEATURES3.3V/0.5A,5V/0.5Aor12V/0.4Aoutputs;Pinandsize-compatiblewithLM7805&LM7812regulatorsUpto95%efficiency–noheatsinksorthermalderatingrequiredTwoSIP-packagesfitexistingTO-220footprints:-Vertical-pinmodelsoccupylessthan0.1squarein.-Optionalhorizontalpinsprovide0.350in.installedheight+7.5-36Vdcoperatinginputrange;Low3mAquiescentcurrentBuilt-infiltercapacitors–noexternalcomponentsrequired–40to+70°Coperationatfullload;Short-circuitprotectionExcellentload(±0.2%)andline(±0.3%)regulationIdealforpoweringinstrumentationfrom9V/12V/24V/28VsuppliesorbatteriesCanbeusedwithunregulateddcsuppliesprotectionMDC_78xxSRSeries.B03Page2of678xxSRSeries3.3V/5V/12VOutputsHigh-EfficiencySwitchingRegulatorswithLM78xxPinoutsTechnicalenquiriesemail:[e-mail],tel:[phone](continued)6.Soldering&HandlingPrecautions:Allunitsaredesignedtobehandsolderedtopc-boardsusingno-cleansolders(+260°C,5secondsmax.).Water-solublesolderscanalsobeused,buttheunitsmustbewashedanddriedusingprocessesappropriatetothetypeofsolderemployed.SeetheMechanicalSpecificationssectionforpin1orientationandrecommendedplated-throughholedimensions.While78SRregulatorseasilywithstanda2kVESDdischargetoanyter-minal(usinghumanbodymodel),theyshouldalwaysbetreatedasESDsensitivedevices.7.Horizontal-PinModels(78XXSRH-C):78XXSRH-Cswitchingregulatorsarepin-compatiblereplacementsforTO-220styleLM78XXlinearregula-torsthatareinstalledwiththeirmetaltabslyingflatonthesurfaceofthepc-board.However,becausethesurfaceofinductorL1on78XXSRH-Cmodelsiselectricallyconductive,itmustnotbeallowedtocomeincon-tactwithanyexposedpc-boardtraces,otherthanpowerground(GND).Whilethe2-mil-thick(0.05mm)polyesterlabelattachedtoL1providessomedegreeofelectricalinsulation(onlyifL1sitsperfectlyflatonthepc-board),itisrecommendedthata0.020”(0.5mm)clear