LDO_DCDC_Charge_Pump的原理比较与不同之处.ppt

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1、VoltageregulatorSimcomHardwareDept.2wangtaoAgendaVoltageregulatorpresentation:AC-ACDC-ACDC-DCAgendaDC-DCVoltageregulatorpresentation:LDOChargepump(inductorlessDC-DC)DC-DC(inductor)LDOLDO(LowDropout)LDOisalinearregulatorDropoutvoltageoutputvoltagewithin100mV,(Vin–Vo

2、ut)minLDOLDOWorkingprinciple:ThevoltagedividedbyresistorsR1&R2iscomparedwiththeinternalreferencevoltagebytheerroramplifierTheMOSFET,whichisconnectedtotheVoutpin,isthendrivenbythesubsequentoutputsignal.TheoutputvoltageattheVoutpiniscontrolled&stabilizedbyasystemofne

3、gativefeedback.LDOparameters•InputVoltageTheminimumVinmustbelargerthanVout+VDO,independentfromtheminimumvaluegivenintheselectiontable.•EfficiencyByneglectingthequiescentcurrent(Iq)oftheLDO,efficiencycanbecalculatedasVout/Vin.LDOparameters•PowerDissipationPD=(Vin–Vo

4、ut)xIout;PDislimitedbypackage.ComparewithstepdownbuckDC-DC,forhigherpowerdissipationorrequirementsforhigherefficiency,recommendbuck.•CapacitorRequirementsTheoutputcapacitorandespeciallyEquivalentSeriesResistance(ESR)arecriticalforstability.•NoiseandPSRRSelectanLDOw

5、ithhighpowersupplyrejectionratio(PSRR)fornoiseimmunityfromtheinputsupplyandlowoutputnoise.SomeLDOhaveabypass(BP)pinforaddingcapacitancetolowertheoutputnoise.LDOparametersCeramicCapacitorEquivalentCircuitEquivalentSeriesResistance(ESR)isacriticalfactorincircuitperfo

6、rmanceCapacitorImpedanceisafunctionof:CapValue,ESRandFrequencyLDOparametersThingstoknowaboutCeramicCaps:ESRisafunctionof:PhysicalsizeLargercasesizecapshavelowerESRMaterialTypeX7R–Best(lowestESR)X5R–GoodY5V–Lowcost(highestESR)Capacitancevs.Frequency:Capacitancevalue

7、becomessmallerasfrequencyincreases(impedancedrops)AgainmaterialtypehasaneffectLDOparametersX7RMaterialMLCCLowerESRLowerimpedanceBetterCapacitancevs.FrequencyGoodTemp.Tolerance(+/-10%)Y5VMaterialMLCCHigherESRHigherimpedancePoorCapacitancevs.FrequencyPoorTemp.Toleran

8、ce(+20/-80%)LDOselection:LOWnoise,HIGHPSRNoenoughPCBarea(inductorless)LowvoltagedropLowcostRegulatorOverviewChargePumpTypesofChargePumpDevices:Ty