1、u Structure:complement switchsu steady state:voltage and current u Dynamic state:Speed and costChapter 3 Digital circuitCg:gate capacitorCd and Cs:junction capacitorsDynamic model of CMOSAny device has input and output capacitors!Dynamic model of CMOSDynamic behaviorWhen state changed,capacitors mus
2、t be charged or uncharged through a resistor!Analyze without resistive load High state:VH=5V Low state:VL=0VFrom H to L:From L to H:nsCRnf10nsCRpr20Dynamic behaviorFrom H to L:fall time ftLHLOUTeVVVV/nsVVtLLff5.85.15.3lnFrom L to H:rise time rtHLHOUTeVVVV/nsVVtHHrr9.165.35.1lnHigh state:VH=?Low stat
3、e:VL=?From H to L:From L to H:?f?rAnalyze with resistive load DC Driven ability 1/Ron Limitation for output current and resistive load.Time constant Ron Time delay and frequency limit.The importance for RonIf Ron in all the transistors are same?Ron will be different for devises and states.The optimi
4、ze design way Make Ron in any devices the same value by adjust transistor width.Ron 1/W;C W;A W.When Routput in any devices should be same:u DC driven ability for any devices are same;u Rise time and fall time of one devices are same;u Delay time of a device will be only rely on its capacitors.The o
5、ptimize design way Fan-in:The input numbers of a single device If we use smaller device for design,we can get better result!ntdFor VLSI design of CMOS devices:1nnAUse parallel design to limit the fan-in 08ttd07142ttd06222ttd72A4620642A4267AThe fan-in should be less than 6!Use parallel design for pos
6、itive output0422 ttd0514 ttd22220A1863 AOutput driven and load on lineWhen output is connected with more than one input,the time delay will be longer!422 FXt4 FXtTime delay on the connected line25.725.34YXt12345FXtTime delay on the connected line25.925.36YXt25.825.35FXtDynamic power consumptionfVCCP
7、PPCCLPDLD2Power consumption is mainly happened when the state is changed!Diode logicOther digital circuit Simple,fast,but the driving ability is weak!Transistor-Transistor Logic:TTL circuitDiode logic-Inverter-Output driverOther digital circuit Emitter-Coupled Logic:ECL circuitfastest,power consumption is the largest!Other digital circuit
