LDO-DCDC-Charge-Pump的原理比较与不同之处

VoltageregulatorSimcomHardwareDept.2wangtaoAgendaVoltageregulatorpresentation:•AC-AC•DC-AC•DC-DCAgendaDC-DCVoltageregulatorpresentation:•LDO•Chargepump(inductorlessDC-DC)•DC-DC(inductor)LDO•LDO(LowDropout)LDOisalinearregulator•Dropoutvoltageoutputvoltagewithin100mV,(Vin–Vout)minLDOLDOWorkingprinciple:ThevoltagedividedbyresistorsR1&R2iscomparedwiththeinternalreferencevoltagebytheerroramplifierTheMOSFET,whichisconnectedtotheVoutpin,isthendrivenbythesubsequentoutputsignal.TheoutputvoltageattheVoutpiniscontrolled&stabilizedbyasystemofnegativefeedback.LDOparameters•InputVoltageTheminimumVinmustbelargerthanVout+VDO,independentfromtheminimumvaluegivenintheselectiontable.•EfficiencyByneglectingthequiescentcurrent(Iq)oftheLDO,efficiencycanbecalculatedasVout/Vin.LDOparameters•PowerDissipationPD=(Vin–Vout)xIout;PDislimitedbypackage.ComparewithstepdownbuckDC-DC,forhigherpowerdissipationorrequirementsforhigherefficiency,recommendbuck.•CapacitorRequirementsTheoutputcapacitorandespeciallyEquivalentSeriesResistance(ESR)arecriticalforstability.•NoiseandPSRRSelectanLDOwithhighpowersupplyrejectionratio(PSRR)fornoiseimmunityfromtheinputsupplyandlowoutputnoise.SomeLDOhaveabypass(BP)pinforaddingcapacitancetolowertheoutputnoise.LDOparametersCeramicCapacitorEquivalentCircuit•EquivalentSeriesResistance(ESR)isacriticalfactorincircuitperformance•CapacitorImpedanceisafunctionof:–CapValue,ESRandFrequencyLDOparametersThingstoknowaboutCeramicCaps:ESRisafunctionof:•Physicalsize•LargercasesizecapshavelowerESR•MaterialTypeX7R–Best(lowestESR)X5R–GoodY5V–Lowcost(highestESR)Capacitancevs.Frequency:•Capacitancevaluebecomessmallerasfrequencyincreases(impedancedrops)•AgainmaterialtypehasaneffectLDOparametersX7RMaterialMLCC•LowerESR•Lowerimpedance•BetterCapacitancevs.Frequency•GoodTemp.Tolerance(+/-10%)Y5VMaterialMLCC•HigherESR•Higherimpedance•PoorCapacitancevs.Frequency•PoorTemp.Tolerance(+20/-80%)LDOselection:•LOWnoise,HIGHPSR•NoenoughPCBarea(inductorless)•Lowvoltagedrop•LowcostRegulatorOverviewChargePumpTypesofChargePumpDevices:TypesofChargepumpdevicesareavailableindifferenttopologies:VoltageDoubling(2X)ChargePumps•Vout=2xVinFractionalChargePumps•Vout=NxVin,whereN=devicemultiplication–Example:Vout=1.5xVinRegulatedOutputChargePumps•Canbe2x,3x,Fractional,etc.VoltageDoubleChargePumpWorkingprinciple:CONTROL/CLOCKC+C-VOUTGNDVINSHDNS1S2S3S4CoutCinCflyVoltagedoublechargepumpblockdiagram(Vout=2xVin)CINCFLYCOUTS1S4S3S2VINVOUT+-+-ICFLYCINVIN++CINCFLYCOUTS1S4S3S2VINVOUT+-+-ICINCFLYCOUTVOUTVIN+-+-+-ChargePumpPhaseCycle1:ChargeCFLYChargePumpPhaseCycle2:BootstrapCFLYtotheOutputVoltageDoubleChargePumpEquivalentCircuitforPhaseCycle1:EquivalentCircuitforPhaseCycle2:FractionalChargePumpWorkingprinciple:S1S2S3S4CFLY1CFLY2CINCOUTCONTROL/OSCILLATORVINVOUTENABLEFractionalChargePumps:•Fractionalchargepumpsofferatechniquetomultiplyaninputvoltagebyanon-integermultiplicationfactor•FractionalchargepumpscanhaveefficiencyadvantagesinlowoutputvoltageapplicationsCINCFLY2COUTVOUTVIN+-+-+-CFLY1+-VIN2VINCINCFLY2COUTVOUTVIN+-+-+-CFLY1+-VIN2VINVIN2EquivalentCircuitforPhaseCycle1:EquivalentCircuitforPhaseCycle2:FractionChargePumpWorks:•Operateswith2switchingcyclephases(sameasavoltagedoublingchargepump)•Two“Flying”capacitorsareused:•InthefirstswitchingcycleCFLY1andCFLY2areconnectedinseriesandplacedacrossVin,whicheffectsavoltagedivideratVc=Vin/2foreach“Fly”capacitor.•InthesecondswitchingcycleCFLY1andCFLY2areconnectedinparallel,thenswitchedtobeinseriesbetweenVinandVout.•Vout=Vin+Vin/2=1.5xVinFractionalChargePumpRegulatedChargePumpWorkingprinciple:CONTROLVREF+-GNDSHDNS1S2S3S4VINCinVOUTCoutC+C-CflyRegulatedChargePumps:•Regulatedchargepumpsarevoltagedoubling,triplingorfractionalchargepumpswithanoutputvoltageregulationsystemandfeedbackcontrol.•Regulatedchargepumpscanprovideastableoutputvoltagefromavariedinputsupply,whichisidealforbatteryoperateddevices.ChargePumpEfficiencyPrimaryitemswhicheffectefficiency:•RDS(ON)oftheMOSFETswitchingdevices-I2RLoss–LowerRDSspecsarebetter•Operatingquiescentcurrent•VinversusVoutforagivenchargepumptopology-Thisappliestoregulatedchargepumps•Typesofexternalcapacitorsused-Cin,CoutandCflyChargePumpEfficiencyEfficiencyofRegulatedChargePumps:•RegulatedVoltageDoublingChargePumpsFixedoutputvoltagelevelInputvoltagemayvarywithinthedeviceoperatingrangeTheinputvoltageisdoubled,thenregulateddowntothedesiredoutputvoltage.•TheoreticalEfficiency==VOUT/2VINExample:VIN=2.8V,VOUT=3.3V,=58.9%Example:VIN=3V,VOUT=4.5V,=75%ChargePumpEfficiencyEfficiencyofFractionalChargePumps:•RegulatedFractionalChargePumpsFixedoutputvoltagelevelInputvoltagemayvarywithinthedeviceoperatingrangeFractionalchargepumpshaveanadvantageinlowvoltageapplicationssincetheInputtoOutputdifferencevoltagetoberegulatedissmall.•TheoreticalEfficiency==VOUT/1.5VINExample:VIN=2.8V,VOUT=3.3V,=78.6%Example:VIN=3V,VOUT=4.5V,100%ExternalcomponentselectionExternalComponentSelection:•Chargepumpdevicestypicallyrequire3to4externalcapacitorsdependinguponcircuittopology.•TheCIN/COUTtoCFLYratiocanrangefrom1:1to10:1•