Application-Specific Integrated Circuits - Addison Wesley

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1、LastEditedbySP14112004INTRODUCTIONTOASICsAnASIC(pronounceda-sick;boldtypefacedefinesanewterm)isanapplication-specificintegratedcircuitatleastthatiswhattheacronymstandsfor.Beforeweanswerthequestionofwhatthatmeanswefirstlookattheevolutionofthesiliconchiporintegratedcircuit(IC).Figure1.1(a)showsanI

2、Cpackage(thisisapin-gridarray,orPGA,shownupsidedown;thepinswillgothroughholesinaprinted-circuitboard).Peopleoftencallthepackageachip,but,asyoucanseeinFigure1.1(b),thesiliconchipitself(moreproperlycalledadie)ismountedinthecavityunderthesealedlid.APGApackageisusuallymadefromaceramicmaterial,butplasti

3、cpackagesarealsocommon.FIGURE1.1Anintegratedcircuit(IC).(a)Apin-gridarray(PGA)package.(b)Thesilicondieorchipisunderthepackagelid.Thephysicalsizeofasilicondievariesfromafewmillimetersonasidetoover1inchonaside,butinsteadweoftenmeasurethesizeofanICbythenumberoflogicgatesorthenumberoftransistorsthatthe

4、ICcontains.Asaunitofmeasureagateequivalentcorrespondstoatwo-inputNANDgate(acircuitthatperformsthelogicfunction,F=A"B).Oftenwejustusethetermgatesinsteadofgateequivalentswhenwearemeasuringchipsizenottobeconfusedwiththegateterminalofatransistor.Forexample,a100k-gateICcontainstheequivalentof100,000two

5、-inputNANDgates.ThesemiconductorindustryhasevolvedfromthefirstICsoftheearly1970sandmaturedrapidlysincethen.Earlysmall-scaleintegration(SSI)ICscontainedafew(1to10)logicgatesNANDgates,NORgates,andsoonamountingtoafewtensoftransistors.Theeraofmedium-scaleintegration(MSI)increasedtherangeofintegratedl

6、ogicavailabletocountersandsimilar,largerscale,logicfunctions.Theeraoflarge-scaleintegration(LSI)packedevenlargerlogicfunctions,suchasthefirstmicroprocessors,intoasinglechip.Theeraofverylarge-scaleintegration(VLSI)nowoffers64-bitmicroprocessors,completewithcachememoryandfloating-pointarithmeticunits

7、welloveramilliontransistorsonasinglepieceofsilicon.AsCMOSprocesstechnologyimproves,transistorscontinuetogetsmallerandICsholdmoreandmoretransistors.Somepeople(especiallyinJapan)usethetermultralargescaleint