AN-1813-TerminalRegulator is Adjustable

1 ApplicationReportSNOA402B October1975 ,allofthe3-terminalpowerICvoltageregulat orshavea ,theireaseofuse,lowcost, ,withtheintroductionoftheLM117,it is possibletousea to37V , ,anadjustableregulatorismoreversatile, V 30V V LogicRegulatorWithElectronicShutdown*..6 7 AdjustingMultipleOn-CardRegulatorsWithSi ngleControl*.. October1975 RevisedMay2013AN-1813-TerminalRegulatori s AdjustableSubmitDocumentationFeedbackCop yright 1975 2013, is packagedin standardTO-3transistorpackagessothatheat sinkingis ,overloadprotectioncircuitryis improved, 3-terminalregulatorcanbeeasilyunderstood byreferringtoFigure1, ,connectedasa unitygainbuffer,drivesa deliveredtotheregulatoroutput(ratherthan ground)eliminatingtheneedfora ,allthecircuitryis designedtooperateoverthe2 V to40V A is ,theoutputoftheregulatoris theadjustmentterminalis grounded,thedeviceactsasa ,a dividerR1andR2is connectedfromtheoutputtogroundasis shownin Figure2.

2 MAthenflowsthroughR2, givenby:(1)The50 A biasingcurrentis smallcomparedto5 mAandcausesonlya smallerrorin ,it is ,programmingcurrentsotherthan5 floating, ,regulationis mAprogrammingcurrentis sufficient;however,worstcaseminimumloadf orcommercialgradepartsrequiresa AdjustableSNOA402B October1975 RevisedMay2013 SubmitDocumentationFeedbackCopyright 1975 2013, Solidtantalum*DischargesC1if outputis theLM117is factorof2 overa 55 C to+150 C ,toinsureadequateoutputcurrentat150 C thecurrentlimitis relativelyhighat25 C, theLM117allowsfulloutputcurrentat15V differentialanddoesnotallowthecurrentlim ittodroptozeroathighinput-to-outputdiffe rentialvoltages, ,includedonthechip,turnstheregulatorOFFw henthechiptemperatureexceedsabout170 C, ,thethermallimitcircuitryrequiredabout7 V newdesignthatis operativedowntoabout2 ,thethermallimitandcurrentlimitcircuitry in theLM117arefunctional,evenif ,asshownin Figure2.

3 Onlyrequirestheadditionoftworesistorsand a October1975 RevisedMay2013AN-1813-TerminalRegulatori s AdjustableSubmitDocumentationFeedbackCop yright 1975 2013, 10 F bypasscapacitor,80dBripplerejectionis F a bypasscapacitoris used,it is sometimesnecessarytoincludeprotectiondio desasdiscussedlater,topreventthecapacito rfromdischargingthroughinternallowcurren tpathsin stablewithnooutputcapacitors,likeanyfeed backcircuit, 1 F solidtantalum(or25 F aluminumelectrolytic) ,it is F short,thereis connectedtoa regulatorandtheinputis shorted, ,theoutputvoltageoftheregulator,andthera teofdecreaseofVIN. IntheLM117,thisdischargepathisthrougha largejunctionthatis abletosustaina F orless,thereis (C2)candischargethrougha a 50 neededforoutputvoltagesof25V andlessthan10 showsanLM117withprotectiondiodesincluded forusewithoutputsgreaterthan25V (2)

4 Somecareshouldbetakenin changein possible, AdjustableSNOA402B October1975 RevisedMay2013 SubmitDocumentationFeedbackCopyright 1975 2013, showsa 0 V to25V V outputrequirestheadditionofa negativesupplysothattheadjustmenttermina lcanbedrivento referenceis usedtoprovidea regulated 10mAprogrammingcurrentis usedsincelabsuppliesareoftenusedwithno-l oad,andtheLM317requiresa minimumoutputoftheLM117makesit ,mostcircuitsdrawonlya , a truezerooutputisdesired,theadjustmentcan bedrivento ;however,thisdoesrequirea ,thenormaloutputvoltagetoleranceof 5%betweenregulatorscancauseasmuchas10%di fferencein digitalcircuitry, showsa methodofadjustingmultipleon-cardregulato rssothatalloutputstrackwithin singledivideris setat10mAtominimizetheeffectsofthe50 A biasingcurrentoftheregulatorsandshouldfu rtherbeincreasedif manyLM117' 1 regulatoris.

5 However, Figure8, a lessthan4 V,soit is powerPNPis ,a smallsquarewaveis levelshiftedandappliedtotheadjustmentter minaloftheregulatorbyR4andC2,causingit V 30V PowerSupply5 SNOA402B October1975 RevisedMay2013AN-1813-TerminalRegulatori s AdjustableSubmitDocumentationFeedbackCop yright 1975 2013, *Minoutput V LogicRegulatorWithElectronicShutdown**Al loutputswithin 100mV Minimumload ** R1 120 takenfromtheoutputthroughR3, speed-up,increasingswitchingspeed, Figure9 providesnoprotectionforQ1in blow-outproofswitchingregulatoris shownin Figure10. ThePNPtransistorhasbeenreplacedbya PNP-NPNcombinationwithLM395' , , ,fixedpowerlossesarea greaterpercentageofthetotaloutputpowerso efficiencyis about30kHzandrippleis about150mV, about50mVandlineregulationabout1%fora 10V asa throughthe100 resistor(R5orR8) ,it canbeconnectedtotheoutputofa linearregulatorsothattheswitchingregulat ormaintainsa V AdjustableSNOA402B October1975 RevisedMay2013 SubmitDocumentationFeedbackCopyright 1975 2013, dependentonelectro-chemicalreactions, necessaryis tosettheoutputoftheLM117atthefloatvoltag eandconnectit mandatorysince, highperformancechargerforgelledelectroli telead-acidbatteriesis shownin Figure11.

6 Thischargerisdesignedtoquicklyrechargea ,thechargingcurrentis ,currenttothebatterydecreasesandwhenthec urrenthasdecreasedto150mA,thechargerswit chestoa dischargedbattery,thestartswitchis notneededsincethechargerwillstartbyitsel f;however,it is includedtoallowtoppingoffevenslightlydis chargedbatteries. Solidtantalum*Core October1975 RevisedMay2013AN-1813-TerminalRegulatori s AdjustableSubmitDocumentationFeedbackCop yright 1975 2013, Solidtantalum*Core BatteryCharger8AN-1813-TerminalRegulator is AdjustableSNOA402B October1975 RevisedMay2013 SubmitDocumentationFeedbackCopyright 1975 2013, pushed, setbyR1, sensedacrossR6andcomparedtoa reference(acrossR2) , ,1 foreachpolarityoftheinputasshownin Figure12, internaltotheLM117is a diodefrominput-to-outputthatconductsthec urrentaroundthedevicewhentheoppositeregu latoris ,thepositiveandnegativepeaksmustbesetsep aratelyfora newICpowervoltageregulatorhasbeendevelop edthatis Adjustable ,in ,reliabilityis increasedin ,minimumstressis ,thedeviceis 100% ,theLM117is madewitha standardICproductionprocessandpackagedin astandardTO-3powerpackage, October1975 RevisedMay2013AN-1813-TerminalRegulatori s AdjustableSubmitDocumentationFeedbackCop yright 1975 2013,TexasInstrumentsIncorporatedIMPORTA NTNOTICET exasInstrumentsIncorporatedanditssubsidi aries(TI)

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