CMOS集成电路-反相器.ppt

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1、DigitalIntegratedCircuitsADesignPerspectiveTheInverterTheCMOSInverter直观综述VinVoutCLVDDCMOSInverterPolysiliconInOutVDDGNDPMOS2lMetal1NMOSContactsNWellTwoInvertersConnectinMetalSharepowerandgroundAbutcellsCMOSInverterFirst-OrderDCAnalysisVOL=0VOH=VDDVM=f(Rn,Rp)VDDVDDVi

2、n5VDDVin50VoutVoutRnRpCMOSInverter暂态相应tpHL=f(Ron.CL)=0.69RonCLVoutVoutRnRpVDDVDDVin5VDDVin50(a)Low-to-high(b)High-to-lowCLCLVoltageTransferCharacteristicPMOS负载线VDSpIDpVGSp=-2.5VGSp=-1VDSpIDnVin=0Vin=1.5VoutIDnVin=0Vin=1.5Vin=VDD+VGSpIDn=-IDpVout=VDD+VDSpVoutIDnVin=VD

3、D+VGSpIDn=-IDpVout=VDD+VDSpCMOSInverter负载特性CMOSInverterVTC开关阈值1001010.80.911.11.21.31.41.51.61.71.8MV(V)Wp/WnVIH和VIL的确定VOHVOLVinVoutVMVILVIHAsimplifiedapproachInverter电压增益CMOS反相器的VTC与电源电压的关系（0.25um工艺）Gain=-1仿真VTC器件参数变化对静态CMOS反相器VTC的影响00.511.522.500.511.522.5Vin(V)Vou

4、t(V)GoodPMOSBadNMOSGoodNMOSBadPMOSNominalPropagationDelay传输延时CMOSInverterPropagationDelay一阶分析CMOSInverterPropagationDelay二阶分析CMOSInvertersPolysiliconInOutMetal1VDDGNDPMOSNMOS1.2mm=2l暂态相应tp=0.69CL(Reqn+Reqp)/2?tpLHtpHL设计减小电容，增加晶体管尺寸注意自载!增加VDD(????)延迟与电压VDDDeviceSizing

5、(forfixedload)Self-loadingeffect:IntrinsiccapacitancesdominateNMOS/PMOSratiotpLHtpHLtpb=Wp/WnImpactofRiseTimeonDelayInverterSizingInverterChainCLIfCLisgiven:Howmanystagesareneededtominimizethedelay?Howtosizetheinverters?Mayneedsomeadditionalconstraints.InOutInverterD

6、elayMinimumlengthdevices,L=0.25mmAssumethatforWP=2WN=2Wsamepull-upandpull-downcurrentsapprox.equalresistancesRN=RPapprox.equalrisetpLHandfalltpHLdelaysAnalyzeasanRCnetworktpHL=(ln2)RNCLtpLH=(ln2)RPCLDelay(D):2WWLoadforthenextstage:InverterwithLoadLoad(CL)DelayAssumpt

7、ions:noload->zerodelayCLtp=kRWCLRWRWWunit=1kisaconstant,equalto0.69InverterwithLoadLoadDelayCintCLDelay=kRW(Cint+CL)=kRWCint+kRWCL=kRWCint(1+CL/Cint)=Delay(Internal)+Delay(Load)CN=CunitCP=2Cunit2WWDelayFormulaCint=gCginwithg1f=CL/Cgin-effectivefanoutR=Runit/W;Cint=W

8、Cunittp0=0.69RunitCunitApplytoInverterChainCLInOut12Ntp=tp1+tp2+…+tpNOptimalTaperingforGivenNDelayequationhasN-1unknowns,Cgin,2–Cgi