IntegratedCircuits集成电路电子信息类专业英语计算机类专业英语.docx

IntegratedCircuits集成电路电子信息类专业英语计算机类专业英语.docx

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IntegratedCircuits集成电路电子信息类专业英语计算机类专业英语

IntegratedCircuits（集成电路）

TheIntegratedCircuit

Digitallogicandelectroniccircuitsderivetheirfunctionalityfromelectronicswitchescalledtransistor.Roughlyspeaking,thetransistorcanbelikenedtoanelectronicallycontrolledvalvewherebyenergyappliedtooneconnectionofthevalveenablesenergytoflowbetweentwootherconnections.Bycombiningmultipletransistors,digitallogicbuildingblockssuchasANDgatesandflip-flopsareformed.Transistors,inturn,aremadefromsemiconductors.Consultaperiodictableofelementsinacollegechemistrytextbook,andyouwilllocatesemiconductorsasagroupofelementsseparatingthemetalsandnonmetals.Theyarecalledsemiconductorsbecauseoftheirabilitytobehaveasbothmetalsandnonmetals.Asemiconductorcanbemadetoconductelectricitylikeametalortoinsulateasanonmetaldoes.Thesedifferingelectricalpropertiescanbeaccuratelycontrolledbymixingthesemiconductorwithsmallamountsofotherelements.Thismixingiscalleddoping.Asemiconductorcanbedopedtocontainmoreelectrons（N-type）orfewerelectrons（P-type）.Examplesofcommonlyusedsemiconductorsaresiliconandgermanium.PhosphorousandboronaretwoelementsthatareusedtodopeN-typeandP-typesilicon,respectively.

Atransistorisconstructedbycreatingasandwichofdifferentlydopedsemiconductorlayers.Thetwomostcommontypesoftransistors,thebipolar-junctiontransistor（BJT）andthefield-effecttransistor（FET）areschematicallyillustratedinFigure2.1.Thisfigureshowsboththesiliconstructuresoftheseelementsandtheirgraphicalsymbolicrepresentationaswouldbeseeninacircuitdiagram.TheBJTshownisanNPNtransistor,becauseitiscomposedofasandwichofN-P-Ndopedsilicon.Whenasmallcurrentisinjectedintothebaseterminal,alargercurrentisenabledtoflowfromthecollectortotheemitter.TheFETshownisanN-channelFET,whichiscomposedoftwoN-typeregionsseparatedbyaP-typesubstrate.Whenavoltageisappliedtotheinsulatedgateterminal,acurrentisenabledtoflowfromthedraintothesource.ItiscalledN-channel,becausethegatevoltageinducesanN-channelwithinthesubstrate,enablingcurrenttoflowbetweentheN-regions.

Anotherbasicsemiconductorstructureisadiode,whichisformedsimplybyajunctionofN-typeandP-typesilicon.Diodesactlikeone-wayvalvesbyconductingcurrentonlyfromPtoN.Specialdiodescanbecreatedthatemitlightwhenavoltageisapplied.Appropriatelyenough,thesecomponentsarecalledlightemittingdiodes,orLEDs.Thesesmalllightsaremanufacturedbythemillionsandarefoundindiverseapplicationsfromtelephonestotrafficlights.

Theresultingsmallchipofsemiconductormaterialonwhichatransistorordiodeisfabricatedcanbeencasedinasmallplasticpackageforprotectionagainstdamageandcontaminationfromtheoutsideworld.Smallwiresareconnectedwithinthispackagebetweenthesemiconductorsandwichandpinsthatprotrudefromthepackagetomakeelectricalcontactwithotherpartsoftheintendedcircuit.Onceyouhaveseveraldiscretetransistors,digitallogiccanbebuiltbydirectlywiringthesecomponentstogether.Thecircuitwillfunction,butanysubstantialamountofdigitallogicwillbeverybulky,becauseseveraltransistorsarerequiredtoimplementeachofthevarioustypesoflogicgates.

Atthetimeoftheinventionofthetransistorin1947byJohnBardeen,WalterBrattain,andWilliamShockley,theonlywaytoassemblemultipletransistorsintoasinglecircuitwastobuyseparatediscretetransistorsandwirethemtogether.In1959,JackKilbyandRobertNoyceindependentlyinventedameansoffabricatingmultipletransistorsonasingleslabofsemiconductormaterial.Theirinventionwouldcometobeknownastheintegratedcircuit,orIC,whichisthefoundationofourmoderncomputerizedworld.AnICissocalledbecauseitintegratesmultipletransistorsanddiodesontothesamesmallsemiconductorchip.Insteadofhavingtosolderindividualwiresbetweendiscretecomponents,anICcontainsmanysmallcomponentsthatarealreadywiredtogetherinthedesiredtopologytoformacircuit.

AtypicalIC,withoutitsplasticorceramicpackage,isasquareorrectangularsilicondiemeasuringfrom2to15mmonanedge.DependingontheleveloftechnologyusedtomanufacturetheIC,theremaybeanywherefromadozentotensofmillionsofindividualtransistorsonthissmallchip.Thisamazingdensityofelectroniccomponentsindicatesthatthetransistorsandthewiresthatconnectthemareextremelysmallinsize.DimensionsonanICaremeasuredinunitsofmicrometers,withonemicrometer（1mm）beingonemillionthofameter.Toserveasareferencepoint,ahumanhairisroughly100mmindiameter.SomemodernICscontaincomponentsandwiresthataremeasuredinincrementsassmallas0.1mm!

Eachyear,researchersandengineershavebeenfindingnewwaystosteadilyreducethesefeaturesizestopackmoretransistorsintothesamesiliconarea,asindicatedinFigure2.2.

WhenanICisdesignedandfabricated,itgenerallyfollowsoneoftwomaintransistortechnologies:

bipolarormetal-oxidesemiconductor（MOS）.BipolarprocessescreateBJTs,whereasMOSprocessescreateFETs.Bipolarlogicwasmorecommonbeforethe1980s,butMOStechnologieshavesinceaccountedthegreatmajorityofdigitallogicICs.N-channelFETsarefabricatedinanNMOSprocess,andP-channelFETsarefabricatedinaPMOSprocess.Inthe1980s,complementary-MOS,orCMOS,becamethedominantprocesstechnologyandremainssotothisday.CMOSICsincorporatebothNMOSandPMOStransistors.

ApplicationSpecificIntegratedCircuit

Anapplication-specificintegratedcircuit（ASIC）isanintegratedcircuit（IC）customizedforaparticularuse,ratherthanintendedforgeneral-purposeuse.Forexample,achipdesignedsolelytorunacellphoneisanASIC.Incontrast,the7400seriesand4000seriesintegratedcircuitsarelogicbuildingblocksthatcanbewiredtogetherforuseinmanydifferentapplications.

Asfeaturesizeshaveshrunkanddesigntoolsimprovedovertheyears,themaximumcomplexity（andhencefunctionality）possibleinanASIChasgrownfrom5,000gatestoover100million.ModernASICsoftenincludeentire32-bitprocessors,memoryblocksincludingROM,RAM,EEPROM,Flashandotherlargebuildingblocks.SuchanASICisoftentermedaSoC（System-on-Chip）.DesignersofdigitalASICsuseahardwaredescriptionlanguage（HDL）,suchasVerilogorVHDL,todescribethefunctionalityofASICs.

Field-programmablegatearrays（FPGA）arethemoderndayequivalentof7400serieslogicandabreadboard,containingprogrammablelogicblocksandprogrammableinterconnectsthatallowthesameFPGAtobeusedinmanydifferentapplications.Forsmallerdesignsand/orlowerproductionvolumes,FPGAsmaybemorecosteffectivethananASICdesign.Thenon-recurringengineeringcost（thecosttosetupthefactorytoproduceaparticularASIC）canrunintohundredsofthousandsofdollars.

ThegeneraltermapplicationspecificintegratedcircuitincludesFPGAs,butmostdesignersuseASIConlyfornon-fieldprogrammabledevicesandmakeadistinctionbetweenASICandFPGAs.

History

TheinitialASICsusedgatearraytechnology.Ferrantiproducedperhapsthefirstgate-array,theULA（UncommittedLogicArray）,around1980.Customizationoccurredbyvaryingthemetalinterconnectmask.ULAshadcomplexitiesofuptoafewthousandgates.Laterversionsbecamemoregeneralized,withdifferentbasediescustomizedbybothmetalandpolysiliconlayers.SomebasediesincludeRAMelements.

Standardcelldesign

Inthemid1980sadesignerwouldchooseanASICmanufacturerandimplementtheirdesignusingthedesigntoolsavailablefromthemanufacturer.Whilethirdpartydesigntoolswereavailable,therewasnotaneffectivelinkfromthethirdpartydesigntoolstothelayoutandactualsemiconductorprocessperformancecharacteristicsofthevariousASICmanufacturers.Mostdesignersendedupusingfactoryspecifictoolstocompletetheimplementationoftheirdesigns.AsolutiontothisproblemthatalsoyieldedamuchhigherdensitydevicewastheimplementationofStandardCells.EveryASICmanufacturercouldcreatefunctionalblockswithknownelectricalcharacteristics,suchaspropagationdelay,capacitanceandinductance;thatcouldalsoberepresentedinthirdpartytools.Standardcelldesignistheutilizationofthesefunctionalblockstoachieveveryhighgatedensityandgoodelectricalperformance.StandardcelldesignfitsbetweenGateArrayandFullCustomdesignintermsofbothitsNRE（Non-RecurringEngineering）andrecurringcomponentcost.

Bythelate1980s,logicsynthesistools,suchasDesignCompiler,becameavailable.SuchtoolscouldcompileHDLdescriptionsintoagate-levelnetlist.Thisenabledastyleofdesigncalledstandard-celldesign.Standard-cellIntegratedCircuits（ICs）aredesignedinthefollowingconceptualstages,althoughthesestagesoverlapsignificantlyinpractice.

Thesesteps,implementedwithalevelofskillcommonintheindustry,almostalwaysproduceafinaldevicethatcorrectlyimplementstheoriginaldesign,unlessflawsarelaterintroducedbythephysicalfabricationprocess.

Ateamofdesignengineersstartswithanon-formalunderstandingoftherequiredfunctionsforanewASIC,usuallyderivedfromrequirementsanalysis.

*ThedesignteamconstructsadescriptionofanASICtoachievethesegoalsusinganHDL.Thisprocessisanalogoustowritingacomputerprograminahigh-levellanguage.ThisisusuallycalledtheRTL（registertransferlevel）design.

*Suitabilityforpurposei