LM2638MotherboardPowerSupplySolutionwitha5-BitProgrammableSwitchingControllerandTwoLinearRegulatorControllersMay1999
LM2638
MotherboardPowerSupplySolutionwitha5-BitProgrammableSwitchingControllerandTwoLinearRegulatorControllers
GeneralDescription
TheLM2638providesacomprehensiveembeddedpowersupplysolutionformotherboardshostinghighperformanceMPUssuchasPentium™II,MII™,K6™-2andothersimilarhighperformanceMPUs.TheLM2638incorporatesa5-bitprogrammable,synchronousbuckswitchingcontrollerandtwohigh-speedlinearregulatorcontrollersina24-pinSOpackage.Inatypicalapplication,theswitchingcontrollersuppliestheMPUcore,andthelinearregulatorcontrollerssupplytheGTL+busandtheclockorgraphicschipcore.Achargepumppinhelpsprovidethenecessaryvoltagetopowerthelinearsectionswhen12VisshutoffduringsystemstandbysuchasSTRmode.
Bothlinearcontrollershaveundervoltagelatch-off.
Features
nProvides3regulatedvoltages
nPowerGoodflagandoutputenablenChargepumppinSwitchingSectionnSynchronousrectification
n5-bitDACprogrammabledownto1.3VnTypical±1%DACtolerance
nSwitchingfrequency:50kHzto1MHznOver-voltageprotection
nTwomethodsofover-currentprotectionnAdaptivenon-overlappingFETgatedrivesnSoftstartwithoutexternalcapacitorLinearSectionnN-FETandNPNdrivecapabilitynUltrafastresponsespeed
nUndervoltagelatch-offat0.63V
nOutputvoltagesdefaultto1.5Vand2.5Vyetadjustable
SwitchingSection—Theswitchingregulatorcontrollerfea-turesanIntel-compatible,5-bitprogrammableoutputvolt-age,over-currentandover-voltageprotection,apowergoodsignal,andalogic-controlledoutputenable.Therearetwouser-selectableover-currentprotectionmethods.Onepro-videsaccurateover-currentprotectionwiththeuseofanex-ternalsenseresistor.Theothersavescostbytakingadvan-tageoftherDS_ONofthehigh-sideFET.Whenthereisanovervoltage,thecontrollerturnsoffthehighsideFETandturnsonthelowside.
LinearSection—Thetwolinearregulatorcontrollersfea-turewidecontrolbandwidth,N-FETandNPNtransistordriv-ingcapabilityandanadjustableoutput.ThewidecontrolbandwidthmakesmeetingtheGTL+bustransientresponserequirementaneasyjob.Inminimumconfiguration,thetwocontrollersdefaultto1.5Vand1.25Vrespectively.
Applications
nEmbeddedpowersuppliesformotherboardsnTripleDC/DCpowersupplies
nProgrammablehighcurrentDC/DCpowersupply
PinConfiguration
24-LeadSOIC
DS101034-1
TopView
OrderNumberLM2638MSeeNSPackageNumberM24B
MII™isatrademarkofCyrixCorporationawhollyownedsubsidiaryofNationalSemiconductorCorporation.Pentium™isatrademarkofIntelCorporation.
K6™isatrademarkofAdvancedMicroDevices,Inc.
©1999NationalSemiconductorCorporationDS101034www.national.com
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AbsoluteMaximumRatings(Note1)
IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheNationalSemiconductorSalesOffice/Distributorsforavailabilityandspecifications.VCCVDDJunctionTemperaturePowerDissipation(Note2)
7V17V150˚C1.6W
StorageTemperatureESDSusceptibility
SolderingTime,Temperature(10sec.)
−65˚Cto+150˚C
3kV300˚C
OperatingRatings(Note1)
VCCJunctionTemperatureRange
4.75Vto5.25V0˚Cto+125˚C
VCC=5V,VDD=12Vunlessotherwisespecified.Typicalsandlimitsappearingin
plaintypeapplyforTA=TJ=+25˚C.Limitsappearinginboldfacetypeapplyoverthe0˚Cto+70˚Crange.SymbolIENICCIQ_VCCIQ_VDDRDS_CPParameter
ENPinInternalPull-upCurrentOperatingVCCCurrentVCCShutdownCurrentVDDShutdownCurrentCPPinResistance
EN=5V,VID=10111
EN=0V,VIDPinsFloatingEN=0V,VIDPinsFloatingHighSideFETLowSideFET
SWITCHINGSECTIONVDACOUTIVIDfOSCDMAXDMINRSNS1RDS_SRCRDS_SINKVCC_TH1VCC_TH2VDAC_IHVDAC_ILGABWEAVRAMP_LVRAMP_HtSSDSTEP_SStPWGDtPWBAD5-BitDACOutputVoltageVIDPinsInternalPull-upCurrent
OscillatorFrequencyMaximumDutyCycleMinimumDutyCycleSNS1PinResistancetoGround
GateDriverResistanceWhenSourcingCurrent
GateDriverResistanceWhenSinkingCurrentVCCPower-On-ResetThreshold
VCCShutdownThresholdDACInputHighVoltageDACInputLowVoltageErrorAmplifierDCGainErrorAmplifierUnityGainBandwidth
RampSignalValleyVoltageRampSignalPeakVoltageSoftStartTime
DutyCycleStepChangeduringSoftStart
PWGDResponseTimePWGDResponseTime
SNS1Risesfrom0VtoRatedOutputVoltage
SNS1FallsfromRatedOutputVoltageto0V
22
7651.253.25409612.58.43.4
1510
3.03.5
1.3
8.5
RT=100kΩRT=25kΩ(Note3)
Conditions
Min60
Typ9061.5410010
Max1407.53
UnitsµAmAmAµAΩ
ElectricalCharacteristics
N−1.5%60204
N90245100010001061.54.03.6
N+1.5%140286
VµAkHz%%
13kΩΩΩ
4.3VVVVdBMHzVVClockCycles%µsµs
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VCC=5V,VDD=12Vunlessotherwisespecified.Typicalsandlimitsappearingin
plaintypeapplyforTA=TJ=+25˚C.Limitsappearinginboldfacetypeapplyoverthe0˚Cto+70˚Crange.(Continued)Symbol
SWITCHINGSECTIONVPWGD_HIPWGDHighTripPoint
%AboveRatedOutputVoltageWhenOutputVoltage↑
%AboveRatedOutputVoltageWhenOutputVoltage↓(Note4)
VPWGD_LOPWGDLowTripPoint
%BelowRatedOutputVoltageWhenOutputVoltage↑%BelowRatedOutputVoltageWhenOutputVoltage↓(Note4)
VOVP_TRPICS+VOCPOver-VoltageTripPointCS+PinSinkCurrentOver-CurrentTripPoint(CS+andCS−DifferentialVoltage)SNS2VoltageOutputResistanceSNS2PinBiasCurrentPWGDHighTripPointPWGDLowTripPointSNS3VoltageOutputResistanceSNS3PinBiasCurrentPWGDHighTripPointPWGDLowTripPoint
WhenRegulating(Note4)(Note4)
WhenRegulating(Note4)(Note4)
VDD=12V,VCC=4.75Vto5.25V,IG3=0mAto20mA%SNS1AboveRatedOutputCS+=5V,CS−=4.8VCS+=2V,CS−Dropsfrom2V
615126415
11.572.69.52518555
13
%
96
%
133524469
%µAmV
Parameter
Conditions
Min
Typ
Max
Units
ElectricalCharacteristics
1.5VLDOCONTROLLERSECTIONVSNS2ROUT2ISNS2VPWGD_HIVPWGD_LOVSNS3ROUT3ISNS3VPWGD_HIVPWGD_LOVDD=12V,VCC=4.75Vto5.25V,IG2=0mAto20mA
1.463
1.5200210.630.44
1.538
VΩµAVV
1.25VLDOCONTROLLERSECTION
1.219
1.2520000.630.44
1.281
VΩµAVV
Note1:AbsoluteMaximumRatingsarelimitsbeyondwhichdamagetothedevicemayoccur.Operatingratingsareconditionsunderwhichthedeviceoperatescorrectly.OperatingRatingsdonotimplyguaranteedperformancelimits.
Note2:Maximumallowablepowerdissipationisafunctionofthemaximumjunctiontemperature,TJMAX,thejunction-to-ambientthermalresistance,θJA,andtheambienttemperature,TA.Themaximumallowablepowerdissipationatanyambienttemperatureiscalculatedusing:PMAX=(TJMAX−TA)/θJA.Thejunction-to-ambientthermalresistance,θJA,forLM2638is78˚C/W.ForaTJMAXof150˚CandTAof25˚C,themaximumallowablepowerdissipationis1.6W.Note3:TheletterNstandsforthetypicaloutputvoltagesappearinginitalicboldfacetypeinTable1.
Note4:TheoutputlevelofthePWGDpinisalogicANDofthepowergoodfunctionoftheswitchingsection,the1.5Vsectionandthe1.25Vsection.Fortheswitch-ingsection,thepowergoodisawindow.Forthetwolinearsections,thepowergoodisathresholdwithsomehysteresis.
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VCC=5V,VDD=12Vunlessotherwisespecified.Typicalsandlimitsappearingin
plaintypeapplyforTA=TJ=+25˚C.Limitsappearinginboldfacetypeapplyoverthe0˚Cto+70˚Crange.(Continued)TABLE1.5-BitDACOutputVoltageTable
(VCC=5V,VDD=12V±5%,TA=25˚C,TestMode)SymbolVDACOUTParameter
5-BitDACOutputVoltagesforDifferentVIDCodes
ConditionsVID4:0=01111VID4:0=01110VID4:0=01101VID4:0=01100VID4:0=01011VID4:0=01010VID4:0=01001VID4:0=01000VID4:0=00111VID4:0=00110VID4:0=00101VID4:0=00100VID4:0=00011VID4:0=00010VID4:0=00001VID4:0=00000VID4:0=11111VID4:0=11110VID4:0=11101VID4:0=11100VID4:0=11011VID4:0=11010VID4:0=11001VID4:0=11000VID4:0=10111VID4:0=10110VID4:0=10101VID4:0=10100VID4:0=10011VID4:0=10010VID4:0=10001VID4:0=10000
Typical
UnitsV
ElectricalCharacteristics
1.301.35
1.401.45
1.501.551.601.65
1.701.75
1.801.85
1.901.95
2.002.05(shutdown)
2.1
2.22.32.42.52.62.7
2.82.93.03.13.2
3.33.43.5
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PinDescription
Pin123456789101112131415161718192021222324
LGPGNDVDDSNS2G2SGNDVCCSNS1CS+CS−CPFREQEAOFBPWGDVID4VID3VID2VID1VID0G3SNS3ENHG
PinName
LowsideN-FETgatedriveroutput.
GroundforthetwoFETdriversoftheswitchingsection.SupplyfortheFETgatedrivers.Usuallytiedto+12V.Feedbackpinforthe1.5Vlinearregulator.
GatedriveoutputfortheexternalN-MOSofthefast1.5Vlinearregulator.Groundforinternalsignalcircuitryandsystemgroundreference.Supplyvoltage.Usually+5V.
Outputvoltagemonitorinputfortheswitchingregulator.Switchingregulatorcurrentsenseinput,positivenode.Switchingregulatorcurrentsenseinput,negativenode.
Chargepump.Outputisasquarewavewith50%dutycycle.AmplitudeisclosetoVCCvoltage.
Switchingfrequencyadjustmentpin.Anexternalresistorisneededtosetthedesiredfrequency.
Outputoftheerroramplifier.Usedforcompensatingtheswitchingregulator.Invertinginputoftheerroramplifier.Usedforcompensatingtheswitchingregulator.OpencollectorPowerGoodsignal.5-BitDACinput,MSB.5-BitDACinput.5-BitDACinput.5-BitDACinput.5-BitDACinput,LSB.
GatedrivepinfortheexternalN-MOSofthe1.25Vlinearregulator.Feedbackpinforthe1.25Vlinearregulator.
OutputEnable.Alogiclowshutsthewholechipdown.HighsideN-FETgatedriveroutput.
PinFunction
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BlockDiagram
DS101034-3
TestCircuit
DS101034-4
FIGURE1.LDOControllerTestCircuit
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TypicalApplication
7
DS101034-2www.national.com
FIGURE2.UsingLM2638toSupplyGTL+Bus(VTT,1.5V,5.6A),2.5VStandby(VCC2_5SBY,2AFullPowerand180mASuspend)and3.3VStandby(VCC3_3SBY,1.5AFullPower,0.5ASuspend)元器件交易网www.cecb2b.com
LM2638MotherboardPowerSupplySolutionwitha5-BitProgrammableSwitchingControllerandTwoLinearRegulatorControllersPhysicalDimensions
inches(millimeters)unlessotherwisenoted
24-LeadSmallOutlinePackage
OrderNumberLM2638MNSPackageNumberM24B
LIFESUPPORTPOLICY
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