Icomp1_SCwww.168dy.com

LM5642,LM5642Xwww.
ti.
comSNVS219K–JUNE2003–REVISEDAPRIL2013LM5642/LM5642XHighVoltage,DualSynchronousBuckConverterwithOscillatorSynchronizationCheckforSamples:LM5642,LM5642X1FEATURESDESCRIPTIONTheLM5642seriesconsistsoftwocurrentmode2TwoSynchronousBuckRegulatorssynchronousbuckregulatorcontrollersoperating180°OutofPhaseOperation180°outofphasewitheachotheratanormal200kHzFixedNominalFrequency:LM5642switchingfrequencyof200kHzfortheLM5642andat375kHzfortheLM5642X.
375kHzFixedNominalFrequency:LM5642XSynchronizableSwitchingFrequencyfrom150OutofphaseoperationreducestheinputRMSripplecurrent,therebysignificantlyreducingtherequiredkHzto250kHzfortheLM5642and200kHztoinputcapacitance.
Theswitchingfrequencycanbe500kHzfortheLM5642Xsynchronizedtoanexternalclockbetween150kHz4.
5Vto36VInputRangeand250kHzfortheLM5642andbetween200kHz50AShutdownCurrentand500kHzfortheLM5642X.
ThetwoswitchingregulatoroutputscanalsobeparalleledtooperateasAdjustableOutputfrom1.
3Vto90%ofVinadual-phase,singleoutputregulator.
0.
04%(Typical)LineandLoadRegulationAccuracyTheoutputofeachchannelcanbeindependentlyadjustedfrom1.
3Vto90%ofVin.
Aninternal5VrailCurrentModeControlwithorwithoutaSenseisalsoavailableexternallyfordrivingbootstrapResistorcircuitry.
IndependentEnable/Soft-startPinsAllowCurrent-modefeedbackcontrolassuresexcellentlineSimpleSequentialStartupConfiguration.
andloadregulationandwideloopbandwidthforConfigurableforSingleOutputParallelexcellentresponsetofastloadtransients.
CurrentisOperation.
(SeeFigure4)sensedacrosseithertheVdsofthetopFETorAdjustableCycle-by-cycleCurrentLimitacrossanexternalcurrent-senseresistorconnectedinserieswiththedrainofthetopFET.
InputUnder-voltageLockoutOutputOver-voltageLatchProtectionTheLM5642featuresanalogsoft-startcircuitrythatisindependentoftheoutputloadandoutputOutputUnder-voltageProtectionwithDelaycapacitancemakingthesoft-startbehaviormoreThermalShutdownpredictableandcontrollablethantraditionalsoft-startSelfDischargeofOutputCapacitorswhenthecircuits.
RegulatorisOFFOver-voltageprotectionisavailableforbothoutputs.
TSSOPandHTSSOP(ExposedPAD)PackagesAUV-DelaypinisalsoavailabletoallowdelayedshutofftimefortheICduringanoutputunder-voltageAPPLICATIONSevent.
EmbeddedComputerSystemsTypicalApplicationCircuitNavigationSystemsTelecomSystemsSet-TopBoxesWebPADPointOfLoadPowerArchitectures1Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
2Alltrademarksarethepropertyoftheirrespectiveowners.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.
Copyright2003–2013,TexasInstrumentsIncorporatedProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
LM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
ti.
comConnectionDiagramFigure1.
TopViewFigure2.
TopViewPINDESCRIPTIONSThepositive(+)KelvinsensefortheinternalcurrentsenseamplifierofChannel1.
UseaseparatetracetoKS1(Pin1)connectthispintothecurrent-sensepoint.
ItshouldbeconnectedtoVINascloseaspossibletothecurrent-senseresistor.
Whennocurrent-senseresistorisused,connectascloseaspossibletothedrainnodeoftheupperMOSFET.
CurrentlimitthresholdsettingforChannel1.
Itsinksaconstantcurrentof9.
9A,whichisconvertedtoavoltageILIM1(Pin2)acrossaresistorconnectedfromthispintoVIN.
ThevoltageacrosstheresistoriscomparedwitheithertheVDSofthetopMOSFETorthevoltageacrosstheexternalcurrentsenseresistortodetermineifanover-currentconditionhasoccurredinChannel1.
CompensationpinforChannel1.
Thisistheoutputoftheinternaltransconductanceerroramplifier.
TheloopCOMP1(Pin3)compensationnetworkshouldbeconnectedbetweenthispinandthesignalground,SGND(Pin8).
Feedbackinputforchannel1.
ConnecttoVOUTthroughavoltagedividertosettheChannel1outputvoltage.
FB1(Pin4)TheswitchingfrequencyoftheLM5642canbesynchronizedtoanexternalclock.
SYNC(Pin5)SYNC=LOW:Freerunningat200kHzforLM5642,andat375kHzforLM5642X.
Channelsare180°outofphase.
SYNC=HIGH:WaitingforexternalclockSYNC=FallingEdge:Channel1HDRVpingoeshigh.
Channel2HDRVpingoeshighafter2.
5sdelay.
ThemaximumSYNCpulsewidthmustbegreaterthan100ns.
ForSYNC=Lowoperation,connectthispintosignalgroundthrougha220kresistor.
AcapacitorfromthispintogroundsetsthedelaytimeforUVP.
Thecapacitorischargedfroma5AcurrentUV_DELAY(Pin6)source.
WhenUV_DELAYchargesto2.
3V(typical),thesystemimmediatelylatchesoff.
Connectingthispintogroundwilldisabletheoutputunder-voltageprotection.
Theoutputofaninternal5VLDOregulatorderivedfromVIN.
ItsuppliestheinternalbiasforthechipandpowersVLIN5(Pin7)thebootstrapcircuitryforgatedrive.
Bypassthispintosignalgroundwithaminimumof4.
7Fceramiccapacitor.
Thegroundconnectionforthesignal-levelcircuitry.
Itshouldbeconnectedtothegroundrailofthesystem.
SGND(Pin8)Channel1enablepin.
ThispinisinternallypulleduptoonediodedropaboveVLIN5.
Pullingthispinbelow1.
2VON/SS1(Pin9)(open-collectortype)turnsoffChannel1.
IfbothON/SS1andON/SS2pinsarepulledbelow1.
2V,thewholechipgoesintoshutdownmode.
Addingacapacitortothispinprovidesasoft-startfeaturethatminimizesinrushcurrentandoutputvoltageovershoot.
Channel2enablepin.
SeethedescriptionforPin9,ON/SS1.
MaybeconnectedtoON/SS1forsimultaneousON/SS2(Pin10)startuporforparalleloperation.
Feedbackinputforchannel2.
ConnecttoVOUTthroughavoltagedividertosettheChannel2outputvoltage.
FB2(Pin11)2SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013PINDESCRIPTIONS(continued)CompensationpinforChannel2.
Thisistheoutputoftheinternaltransconductanceerroramplifier.
TheloopCOMP2(Pin12)compensationnetworkshouldbeconnectedbetweenthispinandthesignalgroundSGND(Pin8).
CurrentlimitthresholdsettingforChannel2.
SeeILIM1(Pin2).
ILIM2(Pin13)Thepositive(+)KelvinsensefortheinternalcurrentsenseamplifierofChannel2.
SeeKS1(Pin1).
KS2(Pin14)Thenegative(-)KelvinsensefortheinternalcurrentsenseamplifierofChannel2.
ConnectthispintothelowsideRSNS2(Pin15)ofthecurrentsenseresistorthatisplacedbetweenVINandthedrainofthetopMOSFET.
WhentheRdsofthetopMOSFETisusedforcurrentsensing,connectthispintothesourceofthetopMOSFET.
AlwaysuseaseparatetracetoformaKelvinconnectiontothispin.
Switch-nodeconnectionforChannel2,whichisconnectedtothesourceofthetopMOSFETofChannel2.
ItSW2(Pin16)servesasthenegativesupplyrailforthetop-sidegatedriver,HDRV2.
Top-sidegate-driveoutputforChannel2.
HDRVisafloatingdriveoutputthatridesonthecorrespondingHDRV2(Pin17)switching-nodevoltage.
Bootstrapcapacitorconnection.
ItservesasthepositivesupplyrailfortheChannel2top-sidegatedrive.
ConnectCBOOT2(Pin18)thispintoVDD2(Pin19)throughadiode,andconnectthelowsideofthebootstrapcapacitortoSW2(Pin16).
ThesupplyrailfortheChannel2low-sidegatedrive.
ConnectedtoVLIN5(Pin7)througha4.
7resistorandVDD2(Pin19)bypassedtopowergroundwithaceramiccapacitorofatleast1F.
TiethispintoVDD1(Pin24).
Low-sidegate-driveoutputforChannel2.
LDRV2(Pin20)Thepowergroundconnectionforbothchannels.
Connecttothegroundrailofthesystem.
PGND(Pin21)Thepowerinputpinforthechip.
Connecttothepositive(+)inputrailofthesystem.
ThispinmustbeconnectedVIN(Pin22)tothesamevoltagerailasthetopFETdrain(orthecurrentsenseresistorwhenused).
Low-sidegate-driveoutputforChannel1.
LDRV1(Pin23)ThesupplyrailforChannel1low-sidegatedrive.
TiethispintoVDD2(Pin19).
VDD1(Pin24)Bootstrapcapacitorconnection.
ThispinservesasthepositivesupplyrailfortheChannel1top-sidegatedrive.
CBOOT1(Pin25)SeeCBOOT2(Pin18).
Top-sidegate-driveoutputforChannel1.
SeeHDRV2(Pin17).
HDRV1(Pin26)Switch-nodeconnectionforChannel1.
SeeSW2(Pin16).
SW1(Pin27)Thenegative(-)KelvinsensefortheinternalcurrentsenseamplifierofChannel1.
SeeRSNS2(Pin15).
RSNS1(Pin28)Thepowergroundconnectionforbothchannels.
Connecttothegroundrailofthesystem.
UseofmultipleviastoPGND(DAP)internalgroundplaneorGNDlayerhelpstodissipateheatgeneratedbyoutputpower.
Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback3ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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comThesedeviceshavelimitedbuilt-inESDprotection.
TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
ABSOLUTEMAXIMUMRATINGS(1)(2)VoltagesfromtheindicatedpinstoSGND/PGND:VIN,ILIM1,ILIM2,KS1,KS20.
3Vto38VSW1,SW2,RSNS1,RSNS20.
3to(VIN+0.
3)VFB1,FB2,VDD1,VDD20.
3Vto6VSYNC,COMP1,COMP2,UVDelay0.
3Vto(VLIN5+0.
3)VON/SS1,ON/SS2(3)0.
3Vto(VLIN5+0.
6)VCBOOT1,CBOOT243VCBOOT1toSW1,CBOOT2toSW20.
3Vto7VLDRV1,LDRV20.
3Vto(VDD+0.
3)VHDRV1toSW1,HDRV2toSW20.
3VHDRV1toCBOOT1,HDRV2toCBOOT2+0.
3VPowerDissipation(TA=25°C)(4)TSSOP1.
1WHTSSOP3.
4WAmbientStorageTemp.
Range65°Cto+150°CSolderingDwellTime,Temp.
(5)Wave4sec,260°CInfrared10sec,240°CVaporPhase75sec,219°CESDRating(6)2kV(1)Absolutemaximumratingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.
OperatingRangeindicatesconditionsforwhichthedeviceisintendedtobefunctional,butdoesnotensurespecificperformancelimits.
Forensuredspecificationsandtestconditions,seetheElectricalCharacteristics.
Theensuredspecificationsapplyonlyforthetestconditions.
Someperformancecharacteristicsmaydegradewhenthedeviceisnotoperatedunderthelistedtestconditions.
(2)IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexasInstrumentsSalesOffice/Distributorsforavailabilityandspecifications.
(3)ON/SS1andON/SS2areinternallypulleduptoonediodedropaboveVLIN5.
Donotapplyanexternalpull-upvoltagetothesepins.
ItmaycausedamagetotheIC.
(4)ThemaximumallowablepowerdissipationiscalculatedbyusingPDMAX=(TJMAX-TA)/θJA,whereTJMAXisthemaximumjunctiontemperature,TAistheambienttemperatureandθJAisthejunction-to-ambientthermalresistanceofthespecifiedpackage.
Thepowerdissipationratingsresultsfromusing125°C,25°C,and90.
6°C/WforTJMAX,TA,andθJArespectively.
AθJAof90.
6°C/Wrepresentstheworst-caseconditionofnoheatsinkingofthe28-pinTSSOP.
TheHTSSOPpackagehasaθJAof29°C/W.
TheHTSSOPpackagethermalratingsresultsfromtheICbeingmountedona4layerJEDECstandardboardusingthesametemperatureconditionsastheTSSOPpackageabove.
Athermalshutdownwilloccurifthetemperatureexceedsthemaximumjunctiontemperatureofthedevice.
(5)Seehttp://www.
ti.
comforothermethodsofsolderingplasticsmall-outlinepackages.
(6)Fortestingpurposes,ESDwasappliedusingthehuman-bodymodel,a100pFcapacitordischargedthrougha1.
5kresistor.
OPERATINGRATINGS(1)VIN(VLIN5tiedtoVIN)4.
5Vto5.
5VVIN(VINandVLIN5separate)5.
5Vto36VJunctionTemperature40°Cto+125°C(1)Absolutemaximumratingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.
OperatingRangeindicatesconditionsforwhichthedeviceisintendedtobefunctional,butdoesnotensurespecificperformancelimits.
Forensuredspecificationsandtestconditions,seetheElectricalCharacteristics.
Theensuredspecificationsapplyonlyforthetestconditions.
Someperformancecharacteristicsmaydegradewhenthedeviceisnotoperatedunderthelistedtestconditions.
4SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013ELECTRICALCHARACTERISTICSUnlessotherwisespecified,VIN=28V,GND=PGND=0V,VLIN5=VDD1=VDD2.
Limitsappearinginboldfacetypeapplyoverthespecifiedoperatingjunctiontemperaturerange,(-40°Cto+125°C,ifnototherwisespecified).
SpecificationsappearinginplaintypearemeasuredusinglowdutycyclepulsetestingwithTA=25°C(1),(2).
Min/Maxlimitsarespecifiedbydesign,test,orstatisticalanalysis.
SymbolParameterConditionsMinTypMaxUnitsSystemΔVOUT/VOUTLoadRegulationVIN=28V,Vcompx=0.
5Vto1.
5V0.
04%LineRegulation5.
5V≤VIN≤36V,Vcompx=1.
25V0.
04%VFB1_FB2FeedbackVoltage5.
5V≤VIN≤36V1.
21541.
23641.
2574V-20°Cto85°C1.
21791.
23641.
2549IVINInputSupplyCurrentVON_SSx>2V1.
12.
0mA5.
5V≤VIN≤36VShutdown(3)50110AVON_SS1=VON_SS2=0VVLIN5VLIN5OutputVoltageIVLIN5=0to25mA,4.
7055.
30V5.
5V≤VIN≤36VVCLosCurrentLimitComparatorVIN=6V±2±7.
0mVOffset(VILIMXVRSNSX)ICLCurrentLimitSinkCurrent8.
49.
911.
4AIss_SC1,Soft-StartSourceCurrentVON_ss1=VON_ss2=1.
5V(on)0.
52.
45.
0AIss_SC2Iss_SK1,Soft-StartSinkCurrentVON_ss1=VON_ss2=1.
5V25.
510AIss_SK2VON_SS1,Soft-StartOnThreshold0.
71.
121.
4VVON_SS2VSSTOSoft-StartTimeout(4)3.
4VThresholdIsc_uvdelayUV_DELAYSourceCurrentUV-DELAY=2V259AIsk_uvdelayUV_DELAYSinkCurrentUV-DELAY=0.
4V0.
20.
481.
2mAVUVDelayUV_DELAYThreshold2.
3VVoltageVUVPFB1,FB2,UnderVoltageAsapercentageofnominaloutputvoltage7580.
786%ProtectionLatchThreshold(fallingedge)Hysteresis3.
7%VOVPVOUTOvervoltageAsapercentagemeasuredatVFB1,VFB2107114122%ShutdownLatchThresholdSwx_RSW1,SW2ON-ResistanceVSW1=VSW2=0.
4V420487560(1)AtypicalisthecenterofcharacterizationdatameasuredwithlowdutycyclepulsetstingatTA=25°C.
Typicalsarenotensured.
(2)Alllimitsarespecified.
Allelectricalcharacteristicshavingroom-temperaturelimitsaretestedduringproductionwithTA=TJ=25°C.
Allhotandcoldlimitsarespecifiedbycorrelatingtheelectricalcharacteristicstoprocessandtemperaturevariationsandapplyingstatisticalprocesscontrol.
(3)Bothswitchingcontrollersareoff.
ThelinearregulatorVLIN5remainson.
(4)WhenSS1andSS2pinsarechargedabovethisvoltageandeitheroftheoutputvoltagesatVout1orVout2isstillbelowtheregulationlimit,theundervoltageprotectionfeatureisinitialized.
Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback5ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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comELECTRICALCHARACTERISTICS(continued)Unlessotherwisespecified,VIN=28V,GND=PGND=0V,VLIN5=VDD1=VDD2.
Limitsappearinginboldfacetypeapplyoverthespecifiedoperatingjunctiontemperaturerange,(-40°Cto+125°C,ifnototherwisespecified).
SpecificationsappearinginplaintypearemeasuredusinglowdutycyclepulsetestingwithTA=25°C(1),(2).
Min/Maxlimitsarespecifiedbydesign,test,orstatisticalanalysis.
SymbolParameterConditionsMinTypMaxUnitsGateDriveICBOOTCBOOTxLeakageCurrentVCBOOT1=VCBOOT2=7V10nAISC_DRVHDRVxandLDRVxSourceVCBOOT1=VCBOOT2=5V,VSWx=0V,0.
5ACurrentHDRVx=LDRVx=2.
5VIsk_HDRVHDRVxSinkCurrentVCBOOTx=VDDx=5V,VSWx=0V,HDRVX0.
8A=2.
5VIsk_LDRVLDRVxSinkCurrentVCBOOTx=VDDx=5V,VSWx=0V,LDRVX1.
1A=2.
5VRHDRVHDRV1&2SourceOn-VCBOOT1=VCBOOT2=5V,3.
1ResistanceVSW1=VSW2=0VHDRV1&2SinkOn-1.
5ResistanceRLDRVLDRV1&2SourceOn-VCBOOT1=VCBOOT2=5V,3.
1ResistanceVSW1=VSW2=0VVDD1=VDD1=5VLDRV1&2SinkOn-1.
1ResistanceOscillatorandSyncControls5.
5≤VIN≤36V,LM5642166200226FoscOscillatorFrequencykHz5.
5≤VIN≤36V,LM5642X311375424Don_maxMaximumOn-DutyCycleVFB1=VFB2=1V,Measuredatpins9698.
9%HDRV1andHDRV2Ton_minMinimumOn-Time166nsSSOT_deltaHDRV1andHDRV2DeltaON/SS1=ON/SS2=2V20250nsOnTimeVHSSYNCPinMinHighInput21.
52VVLSSYNCPinMaxLowInput1.
440.
8VErrorAmplifierIFB1,IFB2FeedbackInputBiasVFB1_FIX=1.
5V,VFB2_FIX=1.
5V80±200nACurrentIcomp1_SC,COMPOutputSourceVFB1_FIX=VFB2_FIX=1V,6127Icomp2_SCCurrentVCOMP1=VCOMP2=1VA-20°Cto85°C18Icomp1_SK,COMPOutputSinkCurrentVFB1_FIX=VFB2_FIX=1.
5Vand6118Icomp2_SKVCOMP1=VCOMP2=0.
5VA-20°Cto85°C18gm1,gm2Transconductance720mhoGISNS1,CurrentSenseAmplifierVCOMPx=1.
25V4.
25.
27.
5GISNS2(1&2)GainVoltageReferencesandLinearVoltageRegulatorsUVLOVLIN5Under-voltageON/SS1,ON/SS2transitionLockoutfromlowtohigh3.
64.
04.
4VThresholdRising6SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013Figure3.
Typical2ChannelApplicationCircuitCopyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback7ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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comFigure4.
TypicalSingleChannelApplicationCircuit8SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013BLOCKDIAGRAMFigure5.
BlockDiagramCopyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback9ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
ti.
comTYPICALPERFORMANCECHARACTERISTICSSoftstartWaveforms(No-LoadBothChannels)UVPStartupWaveform(VIN=24V)Figure6.
Figure7.
Over-CurrentandUVPShutdown(VIN=24V,Io2=0A)ShutdownWaveforms(VIN=24V,No-Load)Figure8.
Figure9.
Ch.
1LoadTransientResponse(VIN=24V,Vo1=1.
8V)Ch.
2LoadTransientResponse(VIN=24V,Vo2=3.
3V)Figure10.
Figure11.
10SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)Ch.
2LoadTransientResponse(VIN=36V,Vo2=3.
3V)Ch.
1LoadTransientResponse(VIN=36V,Vo1=1.
8V)Figure12.
Figure13.
InputSupplyCurrentvsTemperatureInputSupplyCurrentvsVIN(ShutdownModeVIN=28V)ShutdownMode(25°C)Figure14.
Figure15.
VLIN5vsTemperatureVLIN5vsVIN(25°C)Figure16.
Figure17.
Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback11ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
ti.
comTYPICALPERFORMANCECHARACTERISTICS(continued)OperatingFrequencyvsTemperatureFBReferenceVoltagevsTemperature(VIN=28V)Figure18.
Figure19.
ErrorAmplifierTranconductanceGainvsEfficiencyvsLoadCurrentUsingResistorSenseTemperatureCh.
1=1.
8V,Ch.
2=OffFigure20.
Figure21.
12SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)EfficiencyvsLoadCurrentEfficiencyvsLoadCurrentUsingVdsSenseCh.
2=3.
3V,Ch.
1=OffCh.
2=1.
8V,Ch.
2=OffFigure22.
Figure23.
EfficiencyvsLoadCurrentUsingVdsSenseCh.
2=3.
3V,Ch.
1=OffFigure24.
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comOPERATINGDESCRIPTIONSSOFTSTARTTheON/SS1pinhasdualfunctionalityasbothchannelenableandsoftstartcontrol.
ReferringtothesoftstartblockdiagramisshowninFigure25,theLM5642willremaininshutdownmodewhilebothsoftstartpinsaregrounded.
Inanormalapplication(withasoftstartcapacitorconnectedbetweentheON/SS1pinandSGND)softstartfunctionsasfollows:Astheinputvoltagerises(note,IssstartstoflowwhenVIN≥2.
2V),theinternal5VLDOstartsup,andaninternal2.
4Acurrentchargesthesoftstartcapacitor.
Duringsoftstart,theerroramplifieroutputvoltageattheCOMPxpinisclampedat0.
55Vandthedutycycleiscontrolledonlybythesoftstartvoltage.
AstheSSxpinvoltagerampsup,thedutycycleincreasesproportionaltothesoftstartramp,causingtheoutputvoltagetorampup.
Therateatwhichthedutycycleincreasesdependsonthecapacitanceofthesoftstartcapacitor.
Thehigherthecapacitance,theslowertheoutputvoltagerampsup.
Whenthecorrespondingoutputvoltageexceeds98%(typical)ofthesettargetvoltage,theregulatorswitchesfromsoftstarttonormaloperatingmode.
Atthistime,the0.
55Vclampattheoutputoftheerroramplifierreleasesandpeakcurrentfeedbackcontroltakesover.
Onceinpeakcurrentfeedbackcontrolmode,theoutputvoltageoftheerroramplifierwilltravelwithina0.
5Vand2VwindowtoachievePWMcontrol.
SeeFigure26.
Theamountofcapacitanceneededforadesiredsoft-starttimecanbeapproximatedinthefollowingequation:whereIss=2.
4Aforonechanneland4.
8Aifthechannelsareparalleledtssisthedesiredsoft-starttime(1)Finally,(2)Duringsoftstart,over-voltageprotectionandcurrentlimitremainineffect.
TheundervoltageprotectionfeatureisactivatedwhentheON/SSpinexceedsthetimeoutthreshold(3.
4Vtypical).
IftheON/SSxcapacitoristoosmall,thedutycyclemayincreasetoorapidly,causingthedevicetolatchoffduetooutputvoltageovershootabovetheOVPthreshold.
Thisbecomesmorelikelyinapplicationswithlowoutputvoltage,highinputvoltageandlightload.
Acapacitanceof10nFisrecommendedateachsoftstartpintoprovideasmoothmonotonicoutputramp.
Figure25.
Soft-StartandON/OFF14SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013Figure26.
VoltageClampatCOMPxPinFigure27.
OVPandUVPOVERVOLTAGEPROTECTION(OVP)Iftheoutputvoltageoneitherchannelrisesabove113%ofnominal,overvoltageprotectionactivates.
Bothchannelswilllatchoff.
WhentheOVPlatchisset,thehighsideFETdriver,HDRVx,isimmediatelyturnedoffandthelowsideFETdriver,LDRVx,isturnedontodischargetheoutputcapacitorthroughtheinductor.
ToresettheOVPlatch,eithertheinputvoltagemustbecycled,orbothchannelsmustbeswitchedoff(bothON/SSpinspulledlow).
UNDERVOLTAGEPROTECTION(UVP)ANDUVDELAYIftheoutputvoltageoneitherchannelfallsbelow80%ofnominal,undervoltageprotectionactivates.
AsshowninFigure27,anunder-voltageeventwillshutofftheUV_DELAYMOSFET,whichwillallowtheUV_DELAYcapacitortochargewith5A(typical).
IftheUV_DELAYpinvoltagereachesthe2.
3Vthresholdbothchannelswilllatchoff.
UV_DELAYwillthenbedisabledandtheUV_DELAYpinwillreturnto0V.
DuringUVP,boththehighsideandlowsideFETdriverswillbeturnedoff.
IfnocapacitorisconnectedtotheUV_DELAYpin,theUVPlatchwillbeactivatedimmediately.
ToresettheUVPlatch,eithertheinputvoltagemustbecycled,orbothON/SSpinsmustbepulledlow.
TheUVPfunctioncanbedisabledbyconnectingtheUV_DELAYpintoground.
Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback15ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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comTHERMALSHUTDOWNTheLM5642ICwillenterthermalshutdownifthedietemperatureexceeds160°C.
ThetopandbottomFETsofbothchannelswillbeturnedoffimmediately.
Inaddition,bothsoftstartcapacitorswillbegintodischargethroughseparate5.
5Acurrentsinks.
Thevoltageonbothcapacitorswillsettletoapproximately1.
1V,whereitwillremainuntilthethermalshutdownconditionhascleared.
TheICwillreturntonormaloperatingmodewhenthedietemperaturehasfallentobelow146°C.
Atthispointthetwosoftstartcapacitorswillbegintochargewiththeirnormal2.
4Acurrentsources.
Thisallowsacontrolledreturntonormaloperation,similartothesoftstartduringturn-on.
Ifthethermalshutdownconditionclearsbeforethevoltageonthesoftstartcapacitorshasfallento1.
1V,thecapacitorswillfirstbedischargedto1.
1V,andthenimmediatelybeginchargingbackup.
OUTPUTCAPACITORDISCHARGEEachchannelhasanembedded480MOSFETwiththedrainconnectedtotheSWxpin.
ThisMOSFETwilldischargetheoutputcapacitorofitschannelifitschannelisoff,ortheICentersafaultstatecausedbyoneofthefollowingconditions:1.
UVP2.
UVLOIfanoutputovervoltageeventoccurs,theHDRVxwillbeturnedoffandLDRVxwillbeturnedonimmediatelytodischargetheoutputcapacitorsofbothchannelsthroughtheinductors.
BOOTSTRAPDIODESELECTIONThebootstrapdiodeandcapacitorformasupplythatfloatsabovetheswitchnodevoltage.
VLIN5powersthissupply,creatingapproximately5V(minusthediodedrop)whichisusedtopowerthehighsideFETdriversanddriverlogic.
Whenselectingabootstrapdiode,Schottkydiodesarepreferredduetotheirlowforwardvoltagedrop,butcaremustbetakenforcircuitsthatoperateathighambienttemperature.
ThereverseleakageofsomeSchottkydiodescanincreasebymorethan1000xathightemperature,andthisleakagepathcandepletethechargeonthebootstrapcapacitor,starvingthedriverandlogic.
StandardPNjunctiondiodesandfastrectifierdiodescanalsobeused,andthesetypesmaintaintightercontroloverreverseleakagecurrentacrosstemperature.
SWITCHINGNOISEREDUCTIONPowerMOSFETsareveryfastswitchingdevices.
Insynchronousrectifierconverters,therapidincreaseofdraincurrentinthetopFETcoupledwithparasiticinductancewillgenerateunwantedLdi/dtnoisespikesatthesourcenodeoftheFET(SWxnode)andalsoattheVINnode.
Themagnitudeofthisnoisewillincreaseastheoutputcurrentincreases.
Thisparasiticspikenoisemayproduceexcessiveelectromagneticinterference(EMI),andcanalsocauseproblemsindeviceperformance.
Therefore,itmustbesuppressedusingoneofthefollowingmethods.
Whenusingresistorbasedcurrentsensing,itisstronglyrecommendedtoaddR-CfilterstothecurrentsenseamplifierinputsasshowninFigure29.
Thiswillreducethesusceptibilitytoswitchingnoise,especiallyduringheavyloadtransientsandshortontimeconditions.
ThefiltercomponentsshouldbeconnectedascloseaspossibletotheIC.
AsshowninFigure28,addingaresistorinserieswiththeHDRVxpinwillslowdownthegatedrive,thusslowingtheriseandfalltimeofthetopFET,yieldingalongerdraincurrenttransitiontime.
Usuallya3.
3to4.
7resistorissufficienttosuppressthenoise.
TopFETswitchinglosseswillincreasewithhigherresistancevalues.
Smallresistors(1-5ohms)canalsobeplacedinserieswiththeCBOOTxpintoeffectivelyreduceswitchnoderinging.
ACBOOTresistorwillslowtherisetimeoftheFET,whereasaresistoratHDRVwillincreasebothriseandfalltimes.
16SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013Figure28.
HDRVSeriesResistorCURRENTSENSINGANDLIMITINGAsshowninFigure29,theKSxandRSNSxpinsaretheinputsofthecurrentsenseamplifier.
CurrentsensingisaccomplishedeitherbysensingtheVdsofthetopFETorbysensingthevoltageacrossacurrentsenseresistorconnectedfromVINtothedrainofthetopFET.
TheadvantagesofsensingcurrentacrossthetopFETarereducedpartscount,costandpowerloss.
TheRDS-ONofthetopFETisnotasstableovertemperatureandvoltageasasenseresistor,hencegreatcaremustbeusedinlayoutforVDSsensingcircuits.
Atinputvoltagesabove30V,themaximumrecommendedoutputcurrentis5Aperchannel.
Keepingthedifferentialcurrent-sensevoltagebelow200mVensureslinearoperationofthecurrentsenseamplifier.
Therefore,theRDS-ONofthetopFETorthecurrentsenseresistormustbesmallenoughsothatthecurrentsensevoltagedoesnotexceed200mVwhenthetopFETison.
ThereisaleadingedgeblankingcircuitthatforcesthetopFETonforatleast166ns.
Beyondthisminimumontime,theoutputofthePWMcomparatorisusedtoturnoffthetopFET.
Additionally,aminimumvoltageofatleast50mVacrossRsnsisrecommendedtoensureahighSNRatthecurrentsenseamplifier.
Assumingamaximumof200mVacrossRsns,thecurrentsenseresistorcanbecalculatedasfollows:whereImaxisthemaximumexpectedloadcurrent,includingoverloadmultiplier(ie:120%)Iripistheinductorripplecurrent(seeEquation17)(3)TheaboveequationgivesthemaximumallowablevalueforRsns.
ConductionlosseswillincreasewithlargerRsns,thusloweringefficiency.
ThepeakcurrentlimitissetbyanexternalresistorconnectedbetweentheILIMxpinandtheKSxpin.
Aninternal10AcurrentsinkontheILIMxpinproducesavoltageacrosstheresistortosetthecurrentlimitthresholdwhichisthencomparedtothecurrentsensevoltage.
A10nFcapacitoracrossthisresistorisrequiredtofilterunwantednoisethatcouldimproperlytripthecurrentlimitcomparator.
Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback17ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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comFigure29.
CurrentSenseandCurrentLimitCurrentlimitisactivatedwhentheinductorcurrentishighenoughtocausethevoltageattheRSNSxpintobelowerthanthatoftheILIMxpin.
ThistogglestheIlimcomparator,thusturningoffthetopFETimmediately.
ThecomparatorisdisabledwhenthetopFETisturnedoffandduringtheleadingedgeblankingtime.
Theequationforcurrentlimitresistor,Rlim,isasfollows:whereIlimistheloadcurrentatwhichthecurrentlimitcomparatorwillbetripped(4)WhensensingcurrentacrossthetopFET,replaceRsnswiththeRDS-ONoftheFET.
ThiscalculatedRlimvaluespecifiesthattheminimumcurrentlimitwillnotbelessthanImax.
Itisrecommendedthata1%toleranceresistorbeused.
WhensensingacrossthetopFET(VDSsensing),RDS-ONwillshowmorevariationthanacurrent-senseresistor,largelyduetotemperaturevariation.
RDS-ONwillincreaseproportionaltotemperatureaccordingtoaspecifictemperaturecoefficient.
RefertotheFETmanufacturer'sdatasheettodeterminetherangeofRDS-ONvaluesoveroperatingtemperatureorseetheComponentSelectionsection(Equation27)foracalculationofmaximumRDS-ON.
ThiswillpreventRDS-ONvariationsfromprematurelytrippingthecurrentlimitcomparatorastheoperatingtemperatureincreases.
ToensureaccuratecurrentsensingusingVDSsensing,specialattentioninboardlayoutisrequired.
TheKSxandRSNSxpinsrequireseparatetracestoformaKelvinconnectionatthecorrespondingcurrentsensenodes.
Inaddition,thefiltercomponentsR14,R16,C14,C15shouldberemoved.
INPUTUNDERVOLTAGELOCKOUT(UVLO)Theinputunder-voltagelockoutthreshold,whichissensedviatheVLIN5internalLDOoutput,is4.
0V(typical).
Belowthisthreshold,bothHDRVxandLDRVxwillbeturnedoffandtheinternal480MOSFETswillbeturnedontodischargetheoutputcapacitorsthroughtheSWxpins.
WhentheinputvoltageisbelowtheUVLOthreshold,theON/SSpinswillsink5mAtodischargethesoftstartcapacitorsandturnoffbothchannels.
Astheinputvoltageincreasesagainabove4.
0V,UVLOwillbede-activated,andthedevicewillrestartthroughanormalsoftstartphase.
IfthevoltageatVLIN5remainsbelow4.
5V,butabovethe4.
0VUVLOthreshold,thedevicecannotbeensuredtooperatewithinspecification.
Iftheinputvoltageisbetween4.
0Vand5.
2V,theVLIN5pinwillnotregulate,butwillfollowapproximately200mVbelowtheinputvoltage.
18SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013DUAL-PHASEPARALLELOPERATIONInapplicationswithhighoutputcurrentdemand,thetwoswitchingchannelscanbeconfiguredtooperateasatwophaseconvertertoprovideasingleoutputvoltagewithcurrentsharingbetweenthetwoswitchingchannels.
Thisapproachgreatlyreducesthestressandheatontheoutputstagecomponentswhileloweringinputripplecurrent.
Theinductorripplecurrentsalsocanceltoavaryingdegreewhichresultsinloweredoutputripplevoltage.
Figure4showsanexampleofatypicaltwo-phasecircuit.
Becauseprecisioncurrentsenseistheprimarydesigncriteriatoensureaccuratecurrentsharingbetweenthetwochannels,bothchannelsmustuseexternalsenseresistorsforcurrentsensing.
Tominimizetheerrorbetweentheerroramplifiersofthetwochannels,tiethefeedbackpinsFB1andFB2togetherandconnecttoasinglevoltagedividerforoutputvoltagesensing.
Also,tietheCOMP1andCOMP2togetherandconnecttothecompensationnetwork.
ON/SS1andON/SS2mustbetiedtogethertoenableanddisablebothchannelssimultaneously.
EXTERNALFREQUENCYSYNCTheLM5642serieshastheabilitytosynchronizetoexternalsourcesinordertosettheswitchingfrequency.
ThisallowstheLM5642tousefrequenciesfrom150kHzto250kHzandtheLM5642Xtousefrequenciesfrom200kHzto500kHz.
Loweringtheswitchingfrequencyallowsasmallerminimumdutycycle,DMIN,andhenceagreaterrangebetweeninputandoutputvoltage.
Increasingswitchingfrequencyallowstheuseofsmalleroutputinductorsandoutputcapacitors(seeComponentSelection).
Ingeneral,synchronizingalltheswitchingfrequenciesinmulti-convertersystemsmakesfilteringoftheswitchingnoiseeasier.
Thesyncinputcanbefromasystemclock,fromanotherswitchingconverterinthesystem,orfromanyotherperiodicsignalwithalogiclow-levellessthan1.
4Vandalogichighlevelgreaterthan2V.
BothCMOSandTTLlevelinputsareacceptable.
TheLM5642seriesusesafixeddelaybetweenChannel1andChannel2.
Thenominalswitchingfrequencyof200kHzfortheLM5642correspondstoaswitchingperiodof5s.
Channel2alwaysturnsitshigh-sideswitchon2.
5safterChannel1Figure30(a).
Whentheconverterissynchronizedtoafrequencyotherthan200kHz,theswitchingperiodisreducedorincreased,whilethefixeddelaybetweenChannel1andChannel2remainsconstant.
Thephasedifferencebetweenchannelsisthereforenolonger180°.
Attheextremesofthesyncrange,thephasedifferencedropsto135°Figure30(b)andFigure30(c).
Theresultofthislowerphasedifferenceisareductioninthemaximumdutycycleofonechannelthatwillnotoverlapthedutycycleoftheother.
AsshowninInputCapacitorSelectionsection,whenthedutycycleD1forChannel1overlapsthedutycycleD2forChannel2,theinputrmscurrentincreases,requiringmoreinputcapacitorsorinputcapacitorswithhigherripplecurrentratings.
Thenew,reducedmaximumdutycyclecanbecalculatedbymultiplyingthesyncfrequency(inHz)by2.
5x10-6(thefixeddelayinseconds).
ThesamelogicappliestotheLM5642X.
HowevertheLM5642Xhasanominalswitchingfrequencyof375kHzwhichcorrespondstoaperiodof2.
67s.
Thereforechannel2oftheLM5642Xalwaysbeginsit'speriodafter1.
33s.
DMAX=FSYNC*2.
5x10-6(5)Atasyncfrequencyof150kHz,forexample,themaximumdutycycleforChannel1thatwillnotoverlapChannel2wouldbe37.
5%.
At250kHz,itisthedutycycleforChannel2thatisreducedtoaDMAXof37.
5%.
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PeriodFixedDelayExampleComponentSelectionOUTPUTVOLTAGESETTINGTheoutputvoltageforeachchannelissetbytheratioofavoltagedividerasshowninFigure31.
Theresistorvaluescanbedeterminedbythefollowingequation:whereVfb=1.
238V(6)AlthoughincreasingthevalueofR1andR2willincreaseefficiency,thiswillalsodecreaseaccuracy.
Therefore,amaximumvalueisrecommendedforR2inordertokeeptheoutputwithin.
3%ofVnom.
ThismaximumR2valueshouldbecalculatedfirstwiththefollowingequation:where200nAisthemaximumcurrentdrawnbyFBxpin(7)20SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013Figure31.
OutputVoltageSettingExample:Vnom=5V,Vfb=1.
2364V,Ifbmax=200nA.
(8)Choose60K(9)TheCycleSkipandDropoutmodesoftheLM5642seriesregulatetheminimumandmaximumoutputvoltage/dutycyclethattheconvertercandeliver.
BothmodescheckthevoltageattheCOMPpin.
MinimumoutputvoltageisdeterminedbytheCycleSkipComparator.
ThiscircuitryskipsthehighsideFETONpulsewhentheCOMPpinvoltageisbelow0.
5Vatthebeginningofacycle.
Theconverterwillcontinuetoskipeveryotherpulseuntilthedutycycle(andCOMPpinvoltage)riseabove0.
5V,effectivelyhalvingtheswitchingfrequency.
MaximumoutputvoltageisdeterminedbytheDropoutcircuitry,whichskipsthelowsideFETONpulsewhenevertheCOMPpinvoltageexceedstherampvoltagederivedfromthecurrentsense.
Uptothreelowsidepulsesmaybeskippedinarowbeforeaminimumon-timepulsemustbeappliedtothelowsideFET.
Figure32showstherangeofouputvoltage(forIo=3A)withrespecttoinputvoltagethatwillkeeptheconverterfromenteringeitherSkipCycleorDropoutmode.
Forinputvoltagesbelow5.
5V,VLIN5mustbeconnectedtoVinthroughasmallresistor(approximately4.
7ohm).
ThiswillensurethatVLIN5doesnotfallbelowtheUVLOthreshold.
Figure32.
OutputVoltageRangeCopyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback21ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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comOutputCapacitorSelectionInapplicationsthatexhibitlarge,fastloadcurrentswings,theslewrateofsuchaloadcurrenttransientwilllikelybebeyondtheresponsespeedoftheregulator.
Therefore,tomeetvoltagetransientrequirementsduringworst-caseloadtransients,specialconsiderationshouldbegiventooutputcapacitorselection.
ThetotalcombinedESRoftheoutputcapacitorsmustbelowerthanacertainvalue,whilethetotalcapacitancemustbegreaterthanacertainvalue.
Also,inapplicationswherethespecificationofoutputvoltageregulationistightandripplevoltagemustbelow,startingfromtherequiredoutputvoltageripplewilloftenresultinfewerdesigniterations.
ALLOWEDTRANSIENTVOLTAGEEXCURSIONTheallowedoutputvoltageexcursionduringaloadtransient(ΔVc_s)is:where±δ%istheoutputvoltageregulationwindow±ε%istheoutputvoltageinitialaccuracy(10)Example:Vnom=5V,δ%=7%,ε%=3.
4%,Vrip=40mVpeaktopeak.
(11)MAXIMUMESRCALCULATIONUnlesstheriseandfalltimesofaloadtransientareslowerthantheresponsespeedofthecontrolloop,ifthetotalcombinedESR(Re)istoohigh,theloadtransientrequirementwillnotbemet,nomatterhowlargethecapacitance.
ThemaximumallowedtotalcombinedESRis:(12)SincetheripplevoltageisincludedinthecalculationofΔVc_s,theinductorripplecurrentshouldnotbeincludedintheworst-caseloadcurrentexcursion.
Simplyusetheworst-caseloadcurrentexcursionforΔIc_s.
Example:ΔVc_s=160mV,ΔIc_s=3A.
ThenRe_max=53.
3m.
MaximumESRcriterioncanbeusedwhentheassociatedcapacitanceishighenough,otherwisemorecapacitorsthanthenumberdeterminedbythiscriterionshouldbeusedinparallel.
MINIMUMCAPACITANCECALCULATIONInaswitchmodepowersupply,theminimumoutputcapacitanceistypicallydictatedbytheloadtransientrequirement.
Ifthereisnotenoughcapacitance,theoutputvoltageexcursionwillexceedthemaximumallowedvalueevenifthemaximumESRrequirementismet.
Theworst-caseloadtransientisanunloadingtransientthathappenswhentheinputvoltageisthehighestandwhenthecurrentswitchingcyclehasjustfinished.
Thecorrespondingminimumcapacitanceiscalculatedasfollows:(13)NoticeitisalreadyassumedthetotalESR,Re,isnogreaterthanRe_max,otherwisethetermunderthesquarerootwillbeanegativevalue.
Also,itisassumedthatLhasalreadybeenselected,thereforetheminimumLvalueshouldbecalculatedbeforeCminandafterRe(seeInductorSelectionbelow).
Example:Re=20m,Vnom=5V,ΔVc_s=160mV,ΔIc_s=3A,L=8H(14)Generallyspeaking,CmindecreaseswithdecreasingRe,ΔIc_s,andL,butwithincreasingVnomandΔVc_s.
22SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013InductorSelectionThesizeoftheoutputinductorcanbedeterminedfromthedesiredoutputripplevoltage,Vrip,andtheimpedanceoftheoutputcapacitorsattheswitchingfrequency.
Theequationtodeterminetheminimuminductancevalueisasfollows:(15)Intheaboveequation,Reisusedinplaceoftheimpedanceoftheoutputcapacitors.
Thisisbecauseinmostcases,theimpedanceoftheoutputcapacitorsattheswitchingfrequencyisveryclosetoRe.
Inthecaseofceramiccapacitors,replaceRewiththetrueimpedanceattheswitchingfrequency.
Example:Vin=36V,Vo=3.
3V,VRIP=60mV,Re=20m,F=200kHz.
(16)Theactualselectionprocessusuallyinvolvesseveraliterationsofalloftheabovesteps,fromripplevoltageselection,tocapacitorselection,toinductancecalculations.
Boththehighestandthelowestinputandoutputvoltagesandloadtransientrequirementsshouldbeconsidered.
IfaninductancevaluelargerthanLminisselected,makesurethattheCminrequirementisnotviolated.
Priorityshouldbegiventoparametersthatarenotflexibleormorecostly.
Forexample,ifthereareveryfewtypesofcapacitorstochoosefrom,itmaybeagoodideatoadjusttheinductancevaluesothatarequirementof3.
2capacitorscanbereducedto3capacitors.
Sinceinductorripplecurrentisoftenthecriterionforselectinganoutputinductor,itisagoodideatodouble-checkthisvalue.
Theequationis:(17)Alsoimportantistheripplecontent,whichisdefinedbyIrip/Inom.
Generallyspeaking,aripplecontentoflessthan50%isok.
Largerripplecontentwillcausetoomuchpowerlossintheinductor.
Example:Vin=36V,Vo=3.
3V,F=200kHz,L=5H,3AmaxIOUT(18)3Ais100%ripplewhichistoohigh.
Inthiscase,theinductorshouldbereselectedonthebasisofripplecurrent.
Example:40%ripple,40%3A=1.
2A(19)(20)Whenchoosingtheinductor,thesaturationcurrentshouldbehigherthanthemaximumpeakinductorcurrentandtheRMScurrentratingshouldbehigherthanthemaximumloadcurrent.
InputCapacitorSelectionThefactthatthetwoswitchingchannelsoftheLM5642are180°outofphasewillreducetheRMSvalueoftheripplecurrentseenbytheinputcapacitors.
Thiswillhelpextendinputcapacitorlifespanandresultinamoreefficientsystem.
InputcapacitorsmustbeselectedthatcanhandleboththemaximumrippleRMScurrentathighestambienttemperatureaswellasthemaximuminputvoltage.
Inapplicationsinwhichoutputvoltagesarelessthanhalfoftheinputvoltage,thecorrespondingdutycycleswillbelessthan50%.
Thismeanstherewillbenooverlapbetweenthetwochannels'inputcurrentpulses.
Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback23ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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comTheequationforcalculatingthemaximumtotalinputrippleRMScurrentfordutycyclesunder50%is:whereI1ismaximumloadcurrentofChannel1I2isthemaximumloadcurrentofChannel2D1isthedutycycleofChannel1D2isthedutycycleofChannel2(21)Example:Imax_1=3.
6A,Imax_2=3.
6A,D1=0.
42,andD2=0.
275(22)Chooseinputcapacitorsthatcanhandle1.
66ArippleRMScurrentathighestambienttemperature.
Inapplicationswhereoutputvoltagesaregreaterthanhalftheinputvoltage,thecorrespondingdutycycleswillbegreaterthan50%,andtherewillbeoverlappinginputcurrentpulses.
Inputripplecurrentwillbehighestunderthesecircumstances.
TheinputRMScurrentinthiscaseisgivenby:(23)Where,again,I1andI2arethemaximumloadcurrentsofchannel1and2,andD1andD2arethedutycycles.
Thisequationshouldbeusedwhenbothdutycyclesareexpectedtobehigherthan50%.
IftheLM5642isbeingusedwithanexternalclockfrequencyotherthan200kHz,or375kHzfortheLM5642X,theprecedingequationsforinputrmscurrentcanstillbeused.
Theselectionofthefirstequationorthesecondchangesbecauseoverlapcannowoccuratdutycyclesthatarelessthan50%.
FromtheEXTERNALFREQUENCYSYNCsection,themaximumdutycyclethatensuresnooverlapbetweendutycycles(andhenceinputcurrentpulses)is:DMAX=FSYNC*2.
5x10-6(24)Therearenowthreedistinctpossibilitieswhichmustbeconsideredwhenselectingtheequationforinputrmscurrent.
ThefollowingappliesfortheLM5642,andalsotheLM5642Xbyreplacing200kHzwith375kHz:1.
BothdutycyclesD1andD2arelessthanDMAX.
Inthiscase,thefirst,simpleequationcanalwaysbeused.
2.
OnedutycycleisgreaterthanDMAXandtheotherdutycycleislessthanDMAX.
Inthiscase,thesystemdesignercantakeadvantageofthefactthatthesyncfeaturereducesDMAXforonechannel,butlengthensitfortheotherchannel.
ForFSYNC200kHz,D2isreducedtoDMAXwhileD1increasesto(1-DMAX).
ByusingthechannelreducedtoDMAXforthelowerdutycycle,andthechannelthathasbeenincreasedforthehigherdutycycle,thefirst,simplermsinputcurrentequationcanbeused.
3.
BothdutycyclesaregreaterthanDMAX.
Thiscaseisidenticaltoasystemat200kHzwhereeitherdutycycleis50%orgreater.
Someoverlapofdutycyclesisspecified,andhencethesecond,morecomplicatedrmsinputcurrentequationmustbeused.
Inputcapacitorsmustmeettheminimumrequirementsofvoltageandripplecurrentcapacity.
Thesizeofthecapacitorshouldthenbeselectedbasedonholduptimerequirements.
Benchtestingforindividualapplicationsisstillthebestwaytodetermineareliableinputcapacitorvalue.
InputcapacitorsshouldalwaysbeplacedascloseaspossibletothecurrentsenseresistororthedrainofthetopFET.
WhenhighESRcapacitorssuchastantalumareused,a1Fceramiccapacitorshouldbeaddedascloselyaspossibletothehigh-sideFETdrainandlow-sideFETsource.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013MOSFETSelectionBOTTOMFETSELECTIONDuringnormaloperation,thebottomFETisswitchingonandoffatalmostzerovoltage.
Therefore,onlyconductionlossesarepresentinthebottomFET.
ThemostimportantparameterwhenselectingthebottomFETistheon-resistance(RDS-ON).
Thelowertheon-resistance,thelowerthepowerloss.
ThebottomFETpowerlosspeaksatmaximuminputvoltageandloadcurrent.
Theequationforthemaximumallowedon-resistanceatroomtemperatureforagivenFETpackage,is:whereTj_maxisthemaximumallowedjunctiontemperatureintheFETTa_maxisthemaximumambienttemperatureRθjaisthejunction-to-ambientthermalresistanceoftheFETTCisthetemperaturecoefficientoftheon-resistancewhichistypicallyintherangeof4000ppm/°C(25)IfthecalculatedRDS-ON(MAX)issmallerthanthelowestvalueavailable,multipleFETscanbeusedinparallel.
ThiseffectivelyreducestheImaxtermintheaboveequation,thusreducingRDS-ON.
WhenusingtwoFETsinparallel,multiplythecalculatedRDS-ON(MAX)by4toobtaintheRDS-ON(MAX)foreachFET.
InthecaseofthreeFETs,multiplyby9.
(26)IftheselectedFEThasanRdsvaluehigherthan35.
3,thentwoFETswithanRDS-ONlessthan141m(4x35.
3m)canbeusedinparallel.
Inthiscase,thetemperatureriseoneachFETwillnotgotoTj_maxbecauseeachFETisnowdissipatingonlyhalfofthetotalpower.
TOPFETSELECTIONThetopFEThastwotypesoflosses:switchinglossandconductionloss.
Theswitchinglossesmainlyconsistofcrossoverlossandlossesrelatedtothelow-sideFETbodydiodereverserecovery.
Sinceitisratherdifficulttoestimatetheswitchingloss,ageneralstartingpointistoallot60%ofthetopFETthermalcapacitytoswitchinglosses.
Thebestwaytopreciselydetermineswitchinglossesisthroughbenchtesting.
TheequationforcalculatingtheonresistanceofthetopFETisthus:(27)Example:Tj_max=100°C,Ta_max=60°C,Rqja=60°C/W,Vin_min=5.
5V,Vnom=5V,andIload_max=3.
6A.
Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback25ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
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com(28)WhenusingFETsinparallel,thesameguidelinesapplytothetopFETasapplytothebottomFET.
LoopCompensationThegeneralpurposeofloopcompensationistomeetstaticanddynamicperformancerequirementswhilemaintainingstability.
Loopgainiswhatisusuallycheckedtodeterminesmall-signalperformance.
Loopgainisequaltotheproductofcontrol-outputtransferfunctionandthefeedbacktransferfunction(thecompensationnetworktransferfunction).
Generallyspeakingitisdesirabletohavealoopgainslopethatisroughly-20dB/decadefromaverylowfrequencytowellbeyondthecrossoverfrequency.
Thecrossoverfrequencyshouldnotexceedone-fifthoftheswitchingfrequency.
Thehigherthebandwidth,thefastertheloadtransientresponsespeedwillbe.
However,ifthedutycyclesaturatesduringaloadtransient,furtherincreasingthesmallsignalbandwidthwillnothelp.
Sincethecontrol-outputtransferfunctionusuallyhasverylimitedlowfrequencygain,itisagoodideatoplaceapoleinthecompensationatzerofrequency,sothatthelowfrequencygainwillberelativelylarge.
AlargeDCgainmeanshighDCregulationaccuracy(i.
e.
DCvoltagechangeslittlewithloadorlinevariations).
Therestofthecompensationschemedependshighlyontheshapeofthecontrol-outputplot.
Figure33.
Control-OutputTransferFunctionAsshowninFigure33,thecontrol-outputtransferfunctionconsistsofonepole(fp),onezero(fz),andadoublepoleatfn(halftheswitchingfrequency).
Thefollowingcanbedonetocreatea-20dB/decaderoll-offoftheloopgain:Placethefirstpoleat0Hz,thefirstzeroatfp,thesecondpoleatfz,andthesecondzeroatfn.
TheresultingfeedbacktransferfunctionisshowninFigure34.
Figure34.
FeedbackTransferFunction26SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013Thecontrol-outputcornerfrequencies,andthusthedesiredcompensationcornerfrequencies,canbedeterminedapproximatelybythefollowingequations:(29)(30)Sincefpisdeterminedbytheoutputnetwork,itwillshiftwithloading(Ro).
ItisbesttouseaminimumIoutvalueofapproximately100mAwhendeterminingthemaximumRovalue.
Example:Re=20m,Co=100uF,Romax=5V/100mA=50:(31)(32)Firstdeterminetheminimumfrequency(fpmin)ofthepoleacrosstheexpectedloadrange,thenplacethefirstcompensationzeroatorbelowthatvalue.
Oncefpminisdetermined,Rc1shouldbecalculatedusing:whereBisthedesiredgaininV/Vatfp(fz1)gmisthetransconductanceoftheerroramplifierR1andR2arethefeedbackresistors(33)Againvaluearound10dB(3.
3v/v)isgenerallyagoodstartingpoint.
Example:B=3.
3v/v,gm=650m,R1=20kK,R2=60.
4k:(34)BandwidthwillvaryproportionaltothevalueofRc1.
Next,Cc1canbedeterminedwiththefollowingequation:(35)Example:fpmin=995Hz,Rc1=20k:(36)Thecompensationnetwork(Figure35)willalsointroducealowfrequencypolewhichwillbecloseto0Hz.
Asecondpoleshouldalsobeplacedatfz.
ThispolecanbecreatedwithasinglecapacitorCc2andashortedRc2(seeFigure35).
Theminimumvalueforthiscapacitorcanbecalculatedby:(37)Cc2maynotbenecessary,howeveritdoescreateamorestablecontrolloop.
Thisisespeciallyimportantwithhighloadcurrentsandincurrentsharingmode.
Example:fz=80kHz,Rc1=20k:(38)Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback27ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
ti.
comAsecondzerocanalsobeaddedwitharesistorinserieswithCc2.
Ifused,thiszeroshouldbeplacedatfn,wherethecontroltooutputgainrollsoffat-40dB/dec.
Generally,fnwillbewellbelowthe0dBlevelandthuswillhavelittleeffectonstability.
Rc2canbecalculatedwiththefollowingequation:(39)Figure35.
CompensationNetworkPCBLayoutConsiderationsToproduceanoptimalpowersolutionwiththeLM5642series,goodlayoutanddesignofthePCBareasimportantasthecomponentselection.
Thefollowingareseveralguidelinestoaidincreatingagoodlayout.
KELVINTRACESFORSENSELINESWhenusingthecurrentsenseresistortosensetheloadcurrentconnecttheKSpinusingaseparatetracetoVIN,ascloseaspossibletothecurrent-senseresistor.
TheRSNSpinshouldbeconnectedusingaseparatetracetothelow-sideofthecurrentsenseresistor.
Thetracesshouldberunparalleltoeachothertogivecommonmoderejection.
Althoughitcanbedifficultinacompactdesign,thesetracesshouldstayawayfromtheoutputinductorandswitchnodeifpossible,toavoidcouplingstrayfluxfields.
Whenacurrent-senseresistorisnotusedtheKSpinshouldbeconnectedascloseaspossibletothedrainnodeoftheupperMOSFETandtheRSNSpinshouldbeconnectedascloseaspossibletothesourceoftheupperMOSFETusingKelvintraces.
TofurtherhelpminimizenoisepickuponthesenselinesistouseRCfilteringontheKSandRSNSpins.
SEPARATEPGNDANDSGNDGoodlayouttechniquesincludeadedicatedgroundplane,usuallyonaninternallayer.
SignallevelcomponentslikethecompensationandfeedbackresistorsshouldbeconnectedtoasectionofthisinternalSGNDplane.
TheSGNDsectionoftheplaneshouldbeconnectedtothepowergroundatonlyonepoint.
ThebestplacetoconnecttheSGNDandPGNDisrightatthePGNDpin.
.
MINIMIZETHESWITCHNODETheplanethatconnectsthepowerFETsandoutputinductortogetherradiatesmoreEMIasitgetslarger.
Usejustenoughcoppertogivelowimpedancetotheswitchingcurrents,preferablyintheformofawide,butshort,tracerun.
LOWIMPEDANCEPOWERPATHThepowerpathincludestheinputcapacitors,powerFETs,outputinductor,andoutputcapacitors.
KeepthesecomponentsonthesamesideofthePCBandconnectthemwiththicktracesorcopperplanes(shapes)onthesamelayer.
Viasaddresistanceandinductancetothepowerpath,andhaverelativelyhighimpedanceconnectionstotheinternalplanes.
Ifhighswitchingcurrentsmustberoutedthroughviasand/orinternalplanes,usemultipleviasinparalleltoreducetheirresistanceandinductance.
Thepowercomponentsshouldbekeptclosetogether.
Thelongerthepathsthatconnectthem,themoretheyactasantennas,radiatingunwantedEMI.
PleaseseeAN-1229(literaturenumberSNVA054)forfurtherPCBlayoutconsiderations.
28SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
ti.
comSNVS219K–JUNE2003–REVISEDAPRIL2013Table1.
BillOfMaterialsforFigure324Vto1.
8,3.
3VLM5642IDPartNumberTypeSizeParametersQtyVendorU1LM5642DualTSSOP-281TISynchronousControllerQ1,Q4Si4850EYN-MOSFETSO-860V2VishayQ2,Q5Si4840DYN-MOSFETSO-840V2VishayD3BAS40-06SchottkyDiodeSOT-2340V1VishayL1RLF12560T-4R2N100Inductor12.
5x12.
5x6mm4.
2H,7m10A1TDKL2RLF12545T-100M5R1Inductor12.
5x12.
5x4.
5mm10H,12m5.
1A1TDKC1C3216X7R1H105KCapacitor12061F,50V1TDKC3,C4,C14,VJ1206Y101KXXATCapacitor1206100pF,25V3VishayC15C27C2012X5R1C105KCapacitor08051F,16V1TDKC6,C16C5750X5R1H106MCapacitor222010F50V,2.
8A2TDKC9,C236TPD330MCapacitor7.
3x4.
3x3.
8mm330F,6.
3V,10m2SanyoC2,C11,C12,VJ1206Y103KXXATCapacitor120610nF,25V4VishayC13C7,C25,C34VJ1206Y104KXXATCapacitor1206100nF,25V3VishayC19VJ1206Y822KXXATCapacitor12068.
2nF10%1VishayC20VJ1206Y153KXXATCapacitor120615nF10%1VishayC26C3216X7R1C475KCapacitor12064.
7F25V1TDKR1CRCW1206123JResistor120612k5%1VishayR2,R6,R14,CRCW1206100JResistor12061005%1VishayR16R13CRCW1206682JResistor12066.
8k12%1VishayR7,R15WSL-2512.
0101%Resistor251210m1W2VishayR8,R9,R12,CRCW1206000ZResistor120608VishayR17,R18,R21,R31,R32R10CRCW12062261FResistor12062.
26k1%1VishayR23CRCW12068451FResistor12068.
45k1%1VishayR24CRCW12061372FResistor120613.
7k1%1VishayR11,R20CRCW12064991FResistor12064.
99k1%2VishayR19CRCW12068251FResistor12068.
25k1%1VishayR27CRCW12064R7JResistor12064.
75%1VishayR28CRCW1206224JResistor1206220k5%1VishayCopyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback29ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
ti.
comTable2.
BillofMaterialsforFigure430Vto1.
8V,20ALM5642IDPartNumberTypeSizeParametersQtyVendorU1LM5642DualTSSOP-281TISynchronousControllerQ1,Q4Si4850EYN-MOSFETSO-860V2VishayQ2,Q3,Q5,Q6Si4470DYN-MOSFETSO-860V4VishayD3BAS40-06SchottkySOT-2340V1VishayDiodeL1,L2RLF12560T-2R7N110Inductor12.
5x12.
5x6mm2.
7H,4.
5m11.
5A2TDKC1C3216X7R1H105KCapacitor12061F,50V1TDKC10,C24,C27C2012X5R1C105KCapacitor08051F,16V3TDKC6,C16,C28,C5750X5R1H106MCapacitor222010F50V,2.
8A4TDKC30C9,C2316MV1000WXCapacitor10mmD20mmH1000F,16V,22m2SanyoC2,C13VJ1206Y103KXXATCapacitor120610nF,25V2VishayC11VJ1206Y223KXXATCapacitor120622nF,25V1VishayC7,C25,C34VJ1206Y104KXXATCapacitor1206100nF,25V3VishayC19VJ1206Y273KXXATCapacitor120627nF10%1VishayC26C3216X7R1C475KCapacitor12064.
7F25V1TDKR1,R13CRCW1206123JResistor120616.
9k1%1VishayR2,R6,R14,CRCW1206100JResistor12061005%1VishayR16R7,R15WSL-2512.
0101%Resistor251210m1W2VishayR8,R9,R12,CRCW1206000ZResistor120608VishayR17,R18,R21,R31,R32R10CRCW12062261FResistor12062.
26k1%1VishayR11CRCW12064991FResistor12064.
99k1%1VishayR23CRCW12061152FResistor120611.
5k1%1VishayR27CRCW12064R7JResistor12064.
75%1VishayR28CRCW1206224JResistor1206220k5%1Vishay30SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
ti.
comSNVS219K–JUNE2003–REVISEDAPRIL2013Table3.
BillOfMaterialsBasedonFigure3Vin=9-16V,VO1,2=1.
5V,1.
8V,5ALM5642XIDPartNumberTypeSizeParametersQtyVendorU1LM5642XDualTSSOP-281TISynchronousControllerQ1,Q4Si4850EYN-MOSFETSO-860V2VishayQ2,Q5Si4840DYN-MOSFETSO-840V2VishayD3BA54ASchottkyDiodeSOT-2330V1VishayL1,L2RLF12545T-4R2N100Inductor12.
5x12.
5x4.
5mm4.
2H,7m6.
5A2TDKC1C3216X7R1H105KCapacitor12061F,50V1TDKC3,C4,C14,VJ1206Y101KXXATCapacitor1206100pF,25V4VishayC15C27C2012X5R1C105KCapacitor08051F,16V1TDKC6,C28C5750X7R1H106MCapacitor222010F50V,2.
8A2TDKC9,C23C4532X7R0J107MCapacitor1812100F,6.
3V,1m2TDKC2,C11,C12,VJ1206Y103KXXATCapacitor120610nF,25V4VishayC13C7,C25,C34VJ1206Y104KXXATCapacitor1206100nF,25V3VishayC18,C20VJ1206Y473KXXATCapacitor120647nF10%2VishayC26C3216X7R1C475KCapacitor12064.
7F25V1TDKR1,R13CRCW12061912FResistor120619.
1k1%2VishayR2,R6,R14,CRCW1206100JResistor12061005%1VishayR16R7,R15WSL-1206.
0201%Resistor120620m1W2VishayR8,R9,R12,CRCW1206000ZResistor120608VishayR17,R18,R21,R31,R32R10,R19CRCW12061001FResistor12061k1%2VishayR11CRCW12062611FResistor12062.
61k1%1VishayR20CRCW12062321FResistor12062.
32k1%1VishayR22,R24CRCW12063011FResistor12063.
01k1%2VishayR27CRCW12064R7JResistor12064.
75%1VishayR28CRCW1206224JResistor1206220k5%1VishayCopyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback31ProductFolderLinks:LM5642LM5642XLM5642,LM5642XSNVS219K–JUNE2003–REVISEDAPRIL2013www.
ti.
comTable4.
BillOfMaterialsBasedonFigure3Vin=9-16V,VO1,2=3.
3V,5V,5ALM5642XIDPartNumberTypeSizeParametersQtyVendorU1LM5642XDualTSSOP-281TISynchronousControllerQ1,Q4Si4850EYN-MOSFETSO-860V2VishayQ2,Q5Si4840DYN-MOSFETSO-840V2VishayD3BA54ASchottkyDiodeSOT-2330V1VishayL1,L2RLF12545T-5R6N6R1Inductor12.
5x12.
5x4.
5mm5.
6H,9m6.
1A2TDKC1C3216X7R1H105KCapacitor12061F,50V1TDKC3,C4,C14,VJ1206Y101KXXATCapacitor1206100pF,25V4VishayC15C27C2012X5R1C105KCapacitor08051F,16V1TDKC6,C28C5750X7R1H106MCapacitor222010F50V,2.
8A2TDKC9,C23C4532X7R0J107MCapacitor1812100F,6.
3V,1m2TDKC2,C11,C12,VJ1206Y103KXXATCapacitor120610nF,25V4VishayC13C7,C25,C34VJ1206Y104KXXATCapacitor1206100nF,25V3VishayC18,C20VJ1206Y393KXXATCapacitor120639nF10%2VishayC26C3216X7R1C475KCapacitor12064.
7F25V1TDKR1,R13CRCW12061912FResistor120619.
1k1%2VishayR2,R6,R14,CRCW1206100JResistor12061005%1VishayR16R7,R15WSL-1206.
0201%Resistor120620m1W2VishayR8,R9,R12,CRCW1206000ZResistor120608VishayR17,R18,R21,R31,R32R10,R19CRCW12061002FResistor120610k1%2VishayR11CRCW12066191FResistor12066.
19k1%1VishayR20CRCW12063321FResistor12063.
32k1%1VishayR22,R24CRCW12063831FResistor12063.
83k1%2VishayR27CRCW12064R7JResistor12064.
75%1VishayR28CRCW1206224JResistor1206220k5%1Vishay32SubmitDocumentationFeedbackCopyright2003–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM5642LM5642XLM5642,LM5642Xwww.
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comSNVS219K–JUNE2003–REVISEDAPRIL2013REVISIONHISTORYChangesfromRevisionJ(April2013)toRevisionKPageChangedlayoutofNationalDataSheettoTIformat32Copyright2003–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback33ProductFolderLinks:LM5642LM5642XPACKAGEOPTIONADDENDUMwww.
ti.
com11-Jan-2021Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Leadfinish/Ballmaterial(6)MSLPeakTemp(3)OpTemp(°C)DeviceMarking(4/5)SamplesLM5642MH/NOPBACTIVEHTSSOPPWP2848RoHS&GreenSNLevel-1-260C-UNLIMLM5642MHLM5642MHX/NOPBACTIVEHTSSOPPWP282500RoHS&GreenSNLevel-1-260C-UNLIMLM5642MHLM5642MTCNRNDTSSOPPW2848Non-RoHS&GreenCallTICallTI-40to125LM5642MTCLM5642MTC/NOPBACTIVETSSOPPW2848RoHS&GreenSNLevel-3-260C-168HR-40to125LM5642MTCLM5642MTCXNRNDTSSOPPW282500Non-RoHS&GreenCallTICallTI-40to125LM5642MTCLM5642MTCX/NOPBACTIVETSSOPPW282500RoHS&GreenSNLevel-3-260C-168HR-40to125LM5642MTCLM5642XMH/NOPBACTIVEHTSSOPPWP2848RoHS&GreenSNLevel-1-260C-UNLIM-40to125LM5642XMHLM5642XMHX/NOPBACTIVEHTSSOPPWP282500RoHS&GreenSNLevel-1-260C-UNLIM-40to125LM5642XMHLM5642XMT/NOPBACTIVETSSOPPW2848RoHS&GreenSNLevel-3-260C-168HR-40to125LM5642XMTLM5642XMTX/NOPBACTIVETSSOPPW282500RoHS&GreenSNLevel-3-260C-168HR-40to125LM5642XMT(1)Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.
Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.
Samplesmayormaynotbeavailable.
OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)RoHS:TIdefines"RoHS"tomeansemiconductorproductsthatarecompliantwiththecurrentEURoHSrequirementsforall10RoHSsubstances,includingtherequirementthatRoHSsubstancedonotexceed0.
1%byweightinhomogeneousmaterials.
Wheredesignedtobesolderedathightemperatures,"RoHS"productsaresuitableforuseinspecifiedlead-freeprocesses.
TImayreferencethesetypesofproductsas"Pb-Free".
RoHSExempt:TIdefines"RoHSExempt"tomeanproductsthatcontainleadbutarecompliantwithEURoHSpursuanttoaspecificEURoHSexemption.
Green:TIdefines"Green"tomeanthecontentofChlorine(Cl)andBromine(Br)basedflameretardantsmeetJS709Blowhalogenrequirementsof<=1000ppmthreshold.
Antimonytrioxidebasedflameretardantsmustalsomeetthe<=1000ppmthresholdrequirement.
PACKAGEOPTIONADDENDUMwww.
ti.
com11-Jan-2021Addendum-Page2(3)MSL,PeakTemp.
-TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
(4)Theremaybeadditionalmarking,whichrelatestothelogo,thelottracecodeinformation,ortheenvironmentalcategoryonthedevice.
(5)MultipleDeviceMarkingswillbeinsideparentheses.
OnlyoneDeviceMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireDeviceMarkingforthatdevice.
(6)Leadfinish/Ballmaterial-OrderableDevicesmayhavemultiplematerialfinishoptions.
Finishoptionsareseparatedbyaverticalruledline.
Leadfinish/Ballmaterialvaluesmaywraptotwolinesifthefinishvalueexceedsthemaximumcolumnwidth.
ImportantInformationandDisclaimer:TheinformationprovidedonthispagerepresentsTI'sknowledgeandbeliefasofthedatethatitisprovided.
TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.
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InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTItoCustomeronanannualbasis.
TAPEANDREELINFORMATION*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQReelDiameter(mm)ReelWidthW1(mm)A0(mm)B0(mm)K0(mm)P1(mm)W(mm)Pin1QuadrantLM5642MHX/NOPBHTSSOPPWP282500330.
016.
46.
810.
21.
68.
016.
0Q1LM5642MTCXTSSOPPW282500330.
016.
46.
810.
21.
68.
016.
0Q1LM5642MTCX/NOPBTSSOPPW282500330.
016.
46.
810.
21.
68.
016.
0Q1LM5642XMHX/NOPBHTSSOPPWP282500330.
016.
46.
810.
21.
68.
016.
0Q1LM5642XMTX/NOPBTSSOPPW282500330.
016.
46.
810.
21.
68.
016.
0Q1PACKAGEMATERIALSINFORMATIONwww.
ti.
com29-Sep-2019PackMaterials-Page1*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQLength(mm)Width(mm)Height(mm)LM5642MHX/NOPBHTSSOPPWP282500367.
0367.
035.
0LM5642MTCXTSSOPPW282500367.
0367.
038.
0LM5642MTCX/NOPBTSSOPPW282500367.
0367.
038.
0LM5642XMHX/NOPBHTSSOPPWP282500367.
0367.
035.
0LM5642XMTX/NOPBTSSOPPW282500367.
0367.
038.
0PACKAGEMATERIALSINFORMATIONwww.
ti.
com29-Sep-2019PackMaterials-Page2www.
ti.
comPACKAGEOUTLINECTYP6.
66.
21.
1MAX26X0.
6528X0.
300.
192X8.
45TYP0.
200.
090-80.
100.
025.
655.
253.
152.
75(1)0.
25GAGEPLANE0.
70.
5ANOTE39.
89.
6BNOTE44.
54.
34214870/A10/2014PowerPAD-1.
1mmmaxheightPWP0028APLASTICSMALLOUTLINENOTES:1.
Alllineardimensionsareinmillimeters.
Anydimensionsinparenthesisareforreferenceonly.
DimensioningandtolerancingperASMEY14.
5M.
2.
Thisdrawingissubjecttochangewithoutnotice.
3.
Thisdimensiondoesnotincludemoldflash,protrusions,orgateburrs.
Moldflash,protrusions,orgateburrsshallnotexceed0.
15mm,perside.
4.
Thisdimensiondoesnotincludeinterleadflash.
Interleadflashshallnotexceed0.
25mm,perside.
5.
ReferenceJEDECregistrationMO-153,variationAET.
PowerPADisatrademarkofTexasInstruments.
TM1280.
1CAB1514PIN1IDAREASEATINGPLANE0.
1CSEEDETAILADETAILATYPICALSCALE1.
800THERMALPADwww.
ti.
comEXAMPLEBOARDLAYOUT0.
05MAXALLAROUND0.
05MINALLAROUND28X(1.
3)(6.
1)28X(0.
45)(0.
9)TYP28X(1.
5)28X(0.
45)26X(0.
65)(3)(3.
4)NOTE9(5.
5)SOLDERMASKOPENING(9.
7)(1.
3)(1.
3)TYP(5.
8)()TYPVIA0.
2(0.
65)TYP4214870/A10/2014PowerPAD-1.
1mmmaxheightPWP0028APLASTICSMALLOUTLINESOLDERMASKDEFINEDPADLANDPATTERNEXAMPLESCALE:6XHV/ISOLATIONOPTION0.
9CLEARANCECREEPAGEOTHERDIMENSIONSIDENTICALTOIPC-7351TMNOTES:(continued)6.
PublicationIPC-7351mayhavealternatedesigns.
7.
Soldermasktolerancesbetweenandaroundsignalpadscanvarybasedonboardfabricationsite.
8.
Thispackageisdesignedtobesolderedtoathermalpadontheboard.
Formoreinformation,seeTexasInstrumentsliteraturenumbersSLMA002(www.
ti.
com/lit/slma002)andSLMA004(www.
ti.
com/lit/slma004).
9.
Sizeofmetalpadmayvaryduetocreepagerequirement.
METALSOLDERMASKOPENINGNONSOLDERMASKDEFINEDSOLDERMASKDETAILSSOLDERMASKOPENINGMETALUNDERSOLDERMASKSOLDERMASKDEFINEDSYMMSYMMSEEDETAILS1141528METALCOVEREDBYSOLDERMASKSOLDERMASKOPENINGIPC-7351NOMINAL0.
65CLEARANCECREEPAGEwww.
ti.
comEXAMPLESTENCILDESIGN28X(1.
3)28X(0.
45)(6.
1)28X(1.
5)28X(0.
45)26X(0.
65)(3)(5.
5)BASEDON0.
127THICKSTENCIL(5.
8)4214870/A10/2014PowerPAD-1.
1mmmaxheightPWP0028APLASTICSMALLOUTLINE2.
66X4.
770.
1782.
88X5.
160.
1523.
0X5.
5(SHOWN)0.
1273.
55X6.
370.
1SOLDERSTENCILOPENINGSTENCILTHICKNESSSEETABLEFORDIFFERENTOPENINGSFOROTHERSTENCILTHICKNESSESNOTES:(continued)10.
Lasercuttingapertureswithtrapezoidalwallsandroundedcornersmayofferbetterpasterelease.
IPC-7525mayhavealternatedesignrecommendations.
11.
Boardassemblysitemayhavedifferentrecommendationsforstencildesign.
TMSOLDERPASTEEXAMPLEEXPOSEDPAD100%PRINTEDSOLDERCOVERAGEAREASCALE:6XHV/ISOLATIONOPTION0.
9CLEARANCECREEPAGEOTHERDIMENSIONSIDENTICALTOIPC-7351SYMMSYMM1141528BASEDON0.
127THICKSTENCILBYSOLDERMASKMETALCOVEREDIPC-7351NOMINAL0.
65CLEARANCECREEPAGEIMPORTANTNOTICEANDDISCLAIMERTIPROVIDESTECHNICALANDRELIABILITYDATA(INCLUDINGDATASHEETS),DESIGNRESOURCES(INCLUDINGREFERENCEDESIGNS),APPLICATIONOROTHERDESIGNADVICE,WEBTOOLS,SAFETYINFORMATION,ANDOTHERRESOURCES"ASIS"ANDWITHALLFAULTS,ANDDISCLAIMSALLWARRANTIES,EXPRESSANDIMPLIED,INCLUDINGWITHOUTLIMITATIONANYIMPLIEDWARRANTIESOFMERCHANTABILITY,FITNESSFORAPARTICULARPURPOSEORNON-INFRINGEMENTOFTHIRDPARTYINTELLECTUALPROPERTYRIGHTS.
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