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DESCRIPTIONKEYFEATURESTheLX8386/86A/86BseriesICsarepositiveregulatorsdesignedtoprovide1.
5Aoutputcurrent.
Theseregulatorsyieldhigherefficiencythancurrentlyavailabledeviceswithallinternalcircuitrydesignedtooperatedowntoa1Vinput-to-outputdifferential.
Inthisproduct,thedropoutvoltageisfullyspecifiedasafunctionofloadcurrent.
Dropoutisguaranteedatamaximumof1.
3V(LX8386A/86B)and1.
5V(LX8386)atmaximumoutputcurrent,decreasingatlowerloadcurrents.
On-chiptrimmingadjuststhereferencevoltageto1%(0.
8%forthe8386B)initialaccuracyand2%(1%forthe8386B)overline,loadandtemperature.
TheLX8386/86A/86Bseriesdevicesarepin-compatiblewithearlier3-terminalregulators,suchas117seriesproducts.
Whilea10Foutputcapacitorisrequiredonbothinputandoutputofthesenewdevices,thiscapacitorisgenerallyincludedinmostregulatordesigns.
TheLX8386/86A/86Bseriesquiescentcurrentflowsintotheload,increasingefficiency.
ThisfeaturecontrastswithPNPregulators,whereupto10%oftheoutputcurrentiswastedasquiescentcurrent.
TheLX8386-xxIisspecifiedoverthefullindustrialtemperaturerangeof-25°Cto+125°CandtheLX8386/86A/86B-xxCisspecifiedoverthecommercialrangeof0°Cto+125°C.
sssssThree-TerminalAdjustableorFixedOutputsssssGuaranteed40C/Wdependingonmountingtechnique.
THERMALDATABLOCKDIAGRAMThermalLimitCircuitControlCircuitBandgapCircuitOutputCircuitBiasCircuitVOUTVINSOAProtectionCircuitCurrentLimitCircuitADJorGND*321321TABISVOUTTABISVOUT*ThispinGNDforfixedvoltageversions.
3.
VIN2.
VOUT1.
ADJ/GND*DTPACKAGE(D-Pak)(TopView)*Pin1isGNDforfixedvoltageversions.
TABISVOUTVINVOUTADJ/GND*VINVOUTADJ/GND*1.
5ALOWDROPOUTPOSITIVEREGULATORSLX8386-xx/8386A-xx/8386B-xxPRODUCTDATABOOK1996/19973Copyright1999Rev.
1.
7a10/00PRODUCTIONDATASHEETELECTRICALCHARACTERISTICS(Unlessotherwisespecified,thesespecificationsapplyovertheoperatingambienttemperaturesfortheLX8386/86A/86B-xxCwith0°C≤TA≤125°C,andtheLX8386-xxIwith-25°C≤TA≤125°C;VIN-VOUT=3V;IOUT=1.
5A.
Lowdutycyclepulsetestingtechniquesareusedwhichmaintainsjunctionandcasetemperaturesequaltotheambienttemperature.
)ParameterSymbolTestConditionsUnitsLX8386/86A/86B-00Min.
Typ.
Max.
ReferenceVoltageLX8386/86A-00VREFIOUT=10mA,TA=25°C(Note4)10mA≤IOUT≤IOUT(MAX),1.
5V≤(VIN-VOUT),VIN≤10V,P≤PMAXLX8386B-00IOUT=10mA,TA=25°C10mA≤IOUT≤IOUT(MAX),1.
5V≤(VIN-VOUT),VIN≤10V,P≤PMAXLineRegulation(Note2)VREF(VIN)1.
5V≤(VIN-VOUT)≤7V,IOUT=10mALoadRegulation(Note2)VREF(IOUT)VIN-VOUT=3V,10mA≤IOUT≤1.
5AThermalRegulationVOUT(Pwr)TA=25°C,20mspulseRippleRejection(Note3)VOUT=5V,f=120Hz,COUT=100fTantalum,VIN=6.
5VCADJ=10F,IOUT=1.
5AAdjustPinCurrentIADJAdjustPinCurrentChange(Note4)IADJ10mA≤IOUT≤IOUT(MAX),1.
5V≤(VIN-VOUT),VIN≤10VDropoutVoltageLX8386-00VVREF=1%,IOUT=1.
5ALX8386A/86B-00VREF=1%,IOUT=1.
5AMinimumLoadCurrentIOUT(MIN)VIN≤10VMaximumOutputCurrentIOUT(MAX)(VIN-VOUT)≤7VTemperatureStability(Note3)VOUT(T)LongTermStability(Note3)VOUT(t)TA=125°C,1000hoursRMSOutputNoise(%ofVOUT)(Note3)VOUT(RMS)TA=25°C,10Hz≤f≤10kHz1.
2381.
2501.
262V1.
2251.
2501.
270V1.
2401.
2501.
260V1.
2381.
2501.
262V0.
0150.
2%0.
150.
4%0.
010.
04%/W6583dB55100A0.
25A1.
21.
5V1.
11.
3V210mA1.
52.
0A0.
25%0.
31%0.
003%Note2.
Regulationismeasuredatconstantjunctiontemperature,usingpulsetestingwithalowdutycycle.
Changesinoutputvoltageduetoheatingeffectsarecoveredunderthespecificationforthermalregulation.
Note3.
Theseparameters,althoughguaranteed,arenottestedinproduction.
Note4.
SeeMaximumOutputCurrentSectionabove.
ParameterSymbolTestConditionsUnitsLX8386/86A/86B-33Min.
Typ.
Max.
OutputVoltageLX8386-33VOUTVIN=5V,IOUT=0mA,TA=25°C(Note4)4.
75V≤VIN≤10V,0mA≤IOUT≤1.
5A,P≤PMAXLX8386A/86B-33VIN=5V,IOUT=0mA,TA=25°C4.
75V≤VIN≤10V,0mA≤IOUT≤1.
5A,P≤PMAXLineRegulation(Note2)VOUT4.
75V≤VIN≤7V(VIN)4.
75V≤VIN≤10VLoadRegulation(Note2)VOUT(IOUT)VIN=5V,0mA≤IOUT≤IOUT(MAX)ThermalRegulationVOUT(Pwr)TA=25°C,20mspulseRippleRejection(Note3)COUT=100F(Tantalum),IOUT=1.
5AQuiescentCurrentIQ0mA≤IOUT≤IOUT(MAX),4.
75V≤VIN≤10VDropoutVoltageLX8386-33VVOUT=1%,IOUT≤IOUT(MAX)LX8386A/86B-33VOUT=1%,IOUT≤IOUT(MAX)MaximumOutputCurrentIOUT(MAX)VIN≤7VTemperatureStability(Note3)VOUT(T)LongTermStability(Note3)VOUT(t)TA=125°C,1000hoursRMSOutputNoise(%ofVOUT)(Note3)VOUT(RMS)TA=25°C,10Hz≤f≤10kHz3.
2673.
303.
333V3.
2353.
303.
365V3.
2743.
303.
326V3.
2673.
303.
333V16mV210mV515mV0.
010.
02%/W6083dB410mA1.
21.
5V1.
11.
3V1.
52.
0A0.
25%0.
31%0.
003%LX8386/86A/86B-00(Adjustable)LX8386/86A/86B-33(3.
3VFixed)1.
5ALOWDROPOUTPOSITIVEREGULATORSLX8386-xx/8386A-xx/8386B-xxPRODUCTDATABOOK1996/1997Copyright1999Rev.
1.
7a10/004PRODUCTIONDATASHEETAPPLICATIONNOTESTheLX8386/86A/86BseriesICsareeasytouseLow-Dropout(LDO)voltageregulators.
Theyhaveallofthestandardself-protectionfeaturesexpectedofvoltageregulators:shortcircuitprotection,safeoperatingareaprotectionandautomaticthermalshutdownifthedevicetemperaturerisesaboveapproximately165°C.
UseofanoutputcapacitorisREQUIREDwiththeLX8386/86A/86Bseries.
Pleaseseethetablebelowforrecommendedminimumcapacitorvalues.
Theseregulatorsofferamoretightlycontrolledreferencevoltagetoleranceandsuperiorreferencestabilitywhenmeasuredagainsttheolderpin-compatibleregulatortypesthattheyreplace.
STABILITYTheoutputcapacitorispartoftheregulator'sfrequencycompen-sationsystem.
Manytypesofcapacitorsareavailable,withdifferentcapacitancevaluetolerances,capacitancetemperaturecoefficients,andequivalentseriesimpedances.
Foralloperatingconditions,connectionofa220Faluminumelectrolyticcapacitorora47Fsolidtantalumcapacitorbetweentheoutputterminalandgroundwillguaranteestableoperation.
Ifabypasscapacitorisconnectedbetweentheoutputvoltageadjust(ADJ)pinandground,ripplerejectionwillbeimproved(pleaseseethesectionentitled"RIPPLEREJECTION").
WhenADJpinbypassingisused,therequiredoutputcapacitorvalueincreases.
Outputcapacitorvaluesof220F(aluminum)or47F(tantalum)provideforallcasesofbypassingtheADJpin.
IfanADJpinbypasscapacitorisnotused,smalleroutputcapacitorvaluesareadequate.
Thetablebelowshowsrecommendedminimumcapacitancevaluesforstableoperation.
INPUTOUTPUTADJ10F15FTantalum,100FAluminumNone10F47FTantalum,220FAluminum15FInordertoensuregoodtransientresponsefromthepowersupplysystemunderrapidlychangingcurrentloadconditions,designersgenerallyuseseveraloutputcapacitorsconnectedinparallel.
Suchanarrangementservestominimizetheeffectsoftheparasiticresistance(ESR)andinductance(ESL)thatarepresentinallcapacitors.
Cost-effectivesolutionsthatsufficientlylimitESRandESLeffectsgenerallyresultintotalcapacitancevaluesintherangeofhundredstothousandsofmicrofarads,whichismorethanadequatetomeetregulatoroutputcapacitorspecifications.
Outputcapacitancevaluesmaybeincreasedwithoutlimit.
ThecircuitshowninFigure1canbeusedtoobservethetransientresponsecharacteristicsoftheregulatorinapowersystemunderchangingloads.
Theeffectsofdifferentcapacitortypesandvaluesontransientresponseparameters,suchasovershootandunder-shoot,canbequicklycomparedinordertodevelopanoptimumsolution.
RECOMMENDEDCAPACITORVALUESFIGURE1—DynamicInputAndOutputTestLX8386/8386A/8386BPowerSupplyOUTINADJStarGround1sec10msRDSON<TheSOAcircuitlimitstheregulator'smaximumoutputcurrenttoprogres-sivelylowervaluesastheinput-to-outputvoltagedifferenceincreases.
Bylimitingthemaximumoutputcurrent,theSOAcircuitkeepstheamountofpowerthatisdissipatedintheregulatoritselfwithinsafelimitsforallvaluesofinput-to-outputvoltagewithintheoperatingrangeoftheregulator.
TheLX8386/86A/86BSOAprotectionsystemisdesignedtobeabletosupplysomeoutputcurrentforallvaluesofinput-to-outputvoltage,uptothedevicebreakdownvoltage.
Undersomeconditions,acorrectlyoperatingSOAcircuitmaypreventapowersupplysystemfromreturningtoregulatedoperationafterremovalofanintermittentshortcircuitattheoutputoftheregulator.
Thisisanormalmodeofoperationwhichcanbeseeninmostsimilarproducts,includingolderdevicessuchas7800seriesregulators.
Itismostlikelytooccurwhenthepowersysteminputvoltageisrelativelyhighandtheloadimpedanceisrelativelylow.
Whenthepowersystemisstarted"cold",boththeinputandoutputvoltagesareveryclosetozero.
Theoutputvoltagecloselyfollowstherisinginputvoltage,andtheinput-to-outputvoltagedifferenceissmall.
TheSOAcircuitthereforepermitstheregulatortosupplylargeamountsofcurrentasneededtodevelopthedesignedvoltagelevelattheregulatoroutput.
Nowconsiderthecasewheretheregulatorissupplyingregulatedvoltagetoaresistiveloadundersteadystateconditions.
Amoderateinput-to-outputvoltageappearsacrosstheregulatorbutthevoltagedifferenceissmallenoughthattheSOAcircuitryallowssufficientcurrenttoflowthroughtheregulatortodevelopthedesignedoutputvoltageacrosstheloadresistance.
Iftheoutputresistorisshort-circuitedtoground,theinput-to-outputvoltagedifferenceacrosstheregulatorsuddenlybecomeslargerbytheamountofvoltagethathadappearedacrosstheloadresistor.
TheSOAcircuitreadstheincreasedinput-to-outputvoltage,andcutsbacktheamountofcurrentthatitwillpermittheregulatortosupplytoitsoutputterminal.
Whentheshortcircuitacrosstheoutputresistorisremoved,alltheregulatoroutputcurrentwillagainflowthroughtheoutputresistor.
ThemaximumcurrentthattheregulatorcansupplytotheresistorwillbelimitedbytheSOAcircuit,basedonthelargeinput-to-outputvoltageacrosstheregulatoratthetimetheshortcircuitisremovedfromtheoutput.
1.
5ALOWDROPOUTPOSITIVEREGULATORSLX8386-xx/8386A-xx/8386B-xxPRODUCTDATABOOK1996/19975Copyright1999Rev.
1.
7a10/00PRODUCTIONDATASHEETAPPLICATIONNOTESFIGURE2—BasicAdjustableRegulatorR2+R1R1LX8386/86A/86BOUTINADJVOUTVINR1R2VREFIADJ50AVOUT=VREF1++IADJR2R2R1OVERLOADRECOVERY(continued)Ifthislimitedcurrentisnotsufficienttodevelopthedesignedvoltageacrosstheoutputresistor,thevoltagewillstabilizeatsomelowervalue,andwillneverreachthedesignedvalue.
Underthesecircumstances,itmaybenecessarytocycletheinputvoltagedowntozeroinordertomaketheregulatoroutputvoltagereturntoregulation.
RIPPLEREJECTIONRipplerejectioncanbeimprovedbyconnectingacapacitorbetweentheADJpinandground.
ThevalueofthecapacitorshouldbechosensothattheimpedanceofthecapacitorisequalinmagnitudetotheresistanceofR1attheripplefrequency.
Thecapacitorvaluecanbedeterminedbyusingthisequation:C=1/(6.
28*FR*R1)where:C≡thevalueofthecapacitorinFarads;selectanequalorlargerstandardvalue.
FR≡theripplefrequencyinHzR1≡thevalueofresistorR1inohmsAtaripplefrequencyof120Hz,withR1=100:C=1/(6.
28*120Hz*100)=13.
3FTheclosestequalorlargerstandardvalueshouldbeused,inthiscase,15F.
WhenanADJpinbypasscapacitorisused,outputrippleamplitudewillbeessentiallyindependentoftheoutputvoltage.
IfanADJpinbypasscapacitorisnotused,outputripplewillbeproportionaltotheratiooftheoutputvoltagetothereferencevoltage:M=VOUT/VREFwhere:M≡amultiplierfortherippleseenwhentheADJpinisoptimallybypassed.
VREF=1.
25V.
Forexample,ifVOUT=2.
5Vtheoutputripplewillbe:M=2.
5V/1.
25V=2OutputripplewillbetwiceasbadasitwouldbeiftheADJpinweretobebypassedtogroundwithaproperlyselectedcapacitor.
OUTPUTVOLTAGETheLX8386/86A/86BICsdevelopa1.
25Vreferencevoltagebetweentheoutputandtheadjustterminal(SeeFigure2).
Byplacingaresistor,R1,betweenthesetwoterminals,aconstantcurrentiscausedtoflowthroughR1anddownthroughR2tosettheoveralloutputvoltage.
Normallythiscurrentisthespecifiedminimumloadcurrentof10mA.
BecauseIADJisverysmallandconstantwhencomparedwiththecurrentthroughR1,itrepresentsasmallerrorandcanusuallybeignored.
LOADREGULATIONBecausetheLX8386/86A/86Bregulatorsarethree-terminaldevices,itisnotpossibletoprovidetrueremoteloadsensing.
Loadregulationwillbelimitedbytheresistanceofthewireconnectingtheregulatortotheload.
Thedatasheetspecificationforloadregulationismeasuredatthebottomofthepackage.
NegativesidesensingisatrueKelvinconnection,withthebottomoftheoutputdividerreturnedtothenegativesideoftheload.
Althoughitmaynotbeimmediatelyobvious,bestloadregulationisobtainedwhenthetopoftheresistordivider,(R1),isconnecteddirectlytothecaseoftheregulator,nottotheload.
ThisisillustratedinFigure3.
IfR1wereconnectedtotheload,theeffectiveresistancebetweentheregulatorandtheloadwouldbe:RPeff=RP*where:RP≡Actualparasiticlineresistance.
WhenthecircuitisconnectedasshowninFigure3,theparasiticresistanceappearsasitsactualvalue,ratherthanthehigherRPeff.
LX8386/86A/86BOUTINADJVINR1R2RLRPParasiticLineResistanceConnectR1toCaseofRegulatorConnectR2toLoadFIGURE3—ConnectionsForBestLoadRegulation1.
5ALOWDROPOUTPOSITIVEREGULATORSLX8386-xx/8386A-xx/8386B-xxPRODUCTDATABOOK1996/1997Copyright1999Rev.
1.
7a10.
006PRODUCTIONDATASHEETAPPLICATIONNOTESExampleGiven:VIN=5VVOUT=2.
5V,IOUT=1.
5AAmbientTemp.
,TA=50°CRθJT=2.
7°C/WforTO-220Find:ProperHeatSinktokeepIC'sjunctiontemperaturebelow125°C.
**Solution:Thejunctiontemperatureis:TJ=PD(RθJT+RθCS+RθSA)+TAwhere:PD≡Dissipatedpower.
RθJT≡Thermalresistancefromthejunctiontothemountingtabofthepackage.
RθCS≡ThermalresistancethroughtheinterfacebetweentheICandthesurfaceonwhichitismounted.
(1.
0°C/Wat6in-lbsmountingscrewtorque.
)RθSA≡Thermalresistancefromthemountingsurfacetoambient(thermalresistanceoftheheatsink).
TS≡Heatsinktemperature.
First,findthemaximumallowablethermalresistanceoftheheatsink:RθSA=-(RθJT+RθCS)PD=(VIN(MAX)-VOUT)IOUT=(5.
0V-2.
5V)*1.
5A=3.
75WRθSA=-(2.
7°C/W+1.
0°C/W)=16.
3°C/WNext,selectasuitableheatsink.
TheselectedheatsinkmusthaveRθSA≤16.
3°C/W.
Thermalloyheatsink6230BhasRθSA=12.
0°C/W.
Finally,verifythatjunctiontemperatureremainswithinspeci-ficationusingtheselectedheatsink:TJ=3.
75W(2.
7°C/W+1.
0°C/W+12.
0°C/W)+50°C=109°CTJTCTSTARθJTRθCSRθSATJ-TAPD125°C-50°C3.
75W**Althoughthedevicecanoperateupto150°Cjunction,itisrecom-mendedforlongtermreliabilitytokeepthejunctiontemperaturebelow125°Cwheneverpossible.
LOADREGULATION(continued)Evenwhenthecircuitisoptimallyconfigured,parasiticresistancecanbeasignificantsourceoferror.
A20milwidePCtracebuiltfrom1oz.
copper-cladcircuitboardmaterialhasaparasiticresistanceofabout25milliohmsperinchofitslengthatroomtemperature.
Ifa3-terminalregulatorusedtosupply2.
50voltsisconnectedby2inchesofthistracetoaloadwhichdraws1.
5ampsofcurrent,a75millivoltdropwillappearbetweentheregulatorandtheload.
Evenwhentheregulatoroutputvoltageisprecisely2.
50volts,theloadwillonlysee2.
43volts,whichisa3%error.
Itisimportanttokeeptheconnectionbetweentheregulatoroutputpinandtheloadasshortaspossible,andtousewidetracesorheavy-gaugewire.
Theminimumspecifiedoutputcapacitancefortheregulatorshouldbelocatednearthereglatorpackage.
Ifseveralcapacitorsareusedinparalleltoconstructthepowersystemoutputcapaci-tance,anycapacitorsbeyondtheminimumneededtomeetthespecifiedrequirementsoftheregulatorshouldbelocatednearthesectionsoftheloadthatrequirerapidly-changingamountsofcurrent.
Placingcapacitorsnearthesourcesofloadtransientswillhelpensurethatpowersystemtransientresponseisnotimpairedbytheeffectsoftraceimpedance.
Tomaintaingoodloadregulation,widetracesshouldbeusedontheinputsideoftheregulator,especiallybetweentheinputcapacitorsandtheregulator.
InputcapacitorESRmustbesmallenoughthatthevoltageattheinputpindoesnotdropbelowVIN(MIN)duringtransients.
VIN(MIN)=VOUT+VDROPOUT(MAX)where:VIN(MIN)≡thelowestallowableinstantaneousvoltageattheinputpin.
VOUT≡thedesignedoutputvoltageforthepowersupplysystem.
VDROPOUT(MAX)≡thespecifieddropoutvoltagefortheinstalledregulator.
THERMALCONSIDERATIONSTheLX8386/86A/86Bregulatorshaveinternalpowerandthermallimitingcircuitrydesignedtoprotecteachdeviceunderoverloadconditions.
Forcontinuousnormalloadconditions,however,maximumjunctiontemperatureratingsmustnotbeexceeded.
Itisimportanttogivecarefulconsiderationtoallsourcesofthermalresistancefromjunctiontoambient.
Thisincludesjunctiontocase,casetoheatsinkinterface,andheatsinkthermalresistanceitself.
Junction-to-casethermalresistanceisspecifiedfromtheICjunctiontothebacksurfaceofthecasedirectlyoppositethedie.
Thisisthelowestresistancepathforheatflow.
Propermountingisrequiredtoensurethebestpossiblethermalflowfromthisareaofthepackagetotheheatsink.
Thermalcompoundatthecase-to-heat-sinkinterfaceisstronglyrecommended.
Ifthecaseofthedevicemustbeelectricallyisolated,athermallyconductivespacercanbeused,aslongasitsaddedcontributiontothermalresistanceisconsidered.
Notethatthecaseofalldevicesinthisseriesiselectricallyconnectedtotheoutput.
1.
5ALOWDROPOUTPOSITIVEREGULATORSLX8386-xx/8386A-xx/8386B-xxPRODUCTDATABOOK1996/19977Copyright1999Rev.
1.
7a10/00PRODUCTIONDATASHEETTYPICALAPPLICATIONSLX8386/86A/86BOUTINADJ150FVINR23651%10FR11211%C110F**C1improvesripplerejection.
XCshouldbe≈R1atripplefrequency.
VOUT5V(NoteA)FIGURE5—1.
2V-8VAdjustableRegulatorFIGURE4—ImprovingRippleRejectionLX8386/86A/86BOUTINADJVOUT**VINR1121R21kC1*10F*Neededifdeviceisfarfromfiltercapacitors.
**VOUT=1.
25V1+C2100FR2R1(NoteA)FIGURE6—5VRegulatorWithShutdown(NoteA)LX8386/86A/86BOUTINADJ5VVIN1211%10F100F3651%1k1k2N3904TTLOutputNoteA:VIN(MIN)=(IntendedVOUT)+(VDROPOUT(MAX))FIGURE7—Fixed3.
3VOutputRegulatorLX8386/86A/86B-33OUTINGND3.
3VVIN10FTantalumor100FAluminumMin.
15FTantalumor100FAluminumcapacitor.
Maybeincreasedwithoutlimit.
ESRmustbelessthan50m.
PRODUCTIONDATA-InformationcontainedinthisdocumentisproprietarytoLinFinity,andiscurrentasofpublicationdate.
ThisdocumentmaynotbemodifiedinanywaywithouttheexpresswrittenconsentofLinFinity.
Productprocessingdoesnotnecessarilyincludetestingofallparameters.
Linfinityreservestherighttochangetheconfigurationandperformanceoftheproductandtodiscontinueproductatanytime.