CMOS VLSI Design and Circuit Simulation Tasks

Simulation tools are needed to extract the electrical characteristics of your circuit blocks for VLSI. Silicon wafer CMOS VLSI design. CMOS VLSI ... Skiptomaincontent Togglemenubar CadencePCBDesign&Analysis Togglesubmenufor:LearnByTopic 3DECAD/MCADandRigidFlex DesignDataManagement DesignReliability DesignReuseandProductivity HDIandMiniaturization HighSpeedDesignandAnalysis LayoutandRouting Manufacturability RF/MicrowaveDesign SchematicCaptureandCircuitSimulation Signal/PowerIntegrity Togglesubmenufor:DesignInsights E-books&WhitePapers MigrationGuides PCBDesignfromStarttoFinish TechnicalPapers Webinars Togglesubmenufor:ProductVideos AllegroPCBEditor AllegroSystemCapture OrCADPCBDesigner PSpice TrainingVideos Togglesubmenufor:TrainingVideos AllegroPCBEditor OrCADCapture OrCADPCBEditor PSpice LatestBlogs ContactUs Opensearchbox Searchsitewide Closesearchbox RecentSearches SharethisPost SharethisPost Shareonfacebook Shareontwitter Shareonlinkedin Shareonemail Home Blog CMOSVLSIDesignandCircuitSimulationTasks KeyTakeaways CMOSVLSIdesignisbrokenintotwosteps:circuitblockdesignandphysicaldesign. Circuitblockdesigninvolvesconnectingtransistorsintologicblocks,whicharethenintegratedintoalargerintegratedcircuit. SimulationtoolsareneededtoextracttheelectricalcharacteristicsofyourcircuitblocksforVLSI. CMOSVLSIdesignisthefirststepincreatingasiliconwaferwithdozensofICs.CMOS(complementarymetal-oxide-semiconductor)VLSI(very-large-scaleintegration)designhasenabledmassivescalinginavarietyofsemiconductordevices.CombiningtheCMOSprocesswithVLSIhashelpedpushpackagestosmallerlevelswhilekeepingcostsreasonable.WhilenotasdenseandsmallasFinFETtechnology,CMOSstillhasamajorroletoplayinearliertechnologynodes,whicharenotexpectedtobephasedoutanytimesoon.Ifyou’redesigninganewintegratedcircuit,SoC,orothercomponent,itwillmostlikelyneedtobecreatedusingCMOSVLSIdesign.Somethinglike99%ofdigital,analog,andRFintegratedcircuitsaremanufacturedusingCMOSprocesses.AsnewerdesignscontinuethetrendofintegrationandrevisedCMOSarchitecturesarebeingdesignedfortaskslikeembeddedAI,circuitsimulationtasksinCMOScircuitblockswillremaincritical.Herearesomeoftheimportantcircuitsimulationtasksyou’llneedtoperformbeforeintegratingcircuitblocks.GettingStartedwithCMOSVLSIDesignCMOSVLSIdesignislikeamodularapproachtocreatingICs.Smallcircuitblocksareconnectedintolargercircuitblockswhicharethenconnectedatthesystemleveltocreateacompleteintegratedcircuit.Thesesmallercircuitblockscanbeanalog,digital,ormixed-signalcircuits.ThemainchallengeinCMOSVLSIdesignistwofold: Designingandsimulatingsmallcircuitsandlargercircuitblocks. Linkingcircuitblockstogetherintoalargersystem. Thefirstofthesetasksrequiressomebasicfront-endcircuitdesignandsimulationtaskstocreateindividualcircuits;someexamplesareshownbelow.Thesesmallercircuitsthenneedtobecombinedintocircuitblocksthatprovidespecificfunctions.Onceyou’vefinishedcreatingandsimulatingsomelargercircuitblocks,you’llhavetomoveontocreatingalayout,whichintegratesmultiplecircuitblocksintoanentiresystem.DigitalCMOSCircuitBlocksThefoundationaldigitalcircuitblockinCMOSVLSIdesignistheCMOSinverter--asimplecircuitcombiningaPMOSandNMOStransistor:CMOSinvertercircuitaspartofCMOSVLSIdesign.ThisfundamentalcircuitisbasicallyaNOTgate.MOSFETtransistorscanbecombinedinotherwaystoproduceanyotherfundamentallogicgates,whichcanthenbecombinedtoproducelargerlogiccircuits.Dependingonhowthesegatesarecombined,differentfunctionscanbeimplementedonthechip.Integrationalsoneedstohappenatthephysicallevel,wheredifferentinputsandoutputsneedtobeconnectedtogetherinphysicalcircuitdesign.TheexamplebelowshowshowaCMOSinvertercanbephysicallyintegratedintoalargercircuitblock.PhysicaldesignofaCMOSinvertercircuit.AnalogCMOSCircuitBlocksAnalogbuildingblockscanalsobebuiltfromCMOScircuitry,andmanymodernproductsarebasedonprovendecades-oldcircuitdesigns.IfaCMOSICincludesanoperationalamplifierorintegratedpowerregulator,itisprobablybuiltonaCMOScircuitthatwasfirstdesigneddecadesearlier.Today,newerdesignsaremakinggreateruseofcustomCMOScircuitryforanalogsignalprocessingatthechiplevel,ratherthanconvertingthesignaltoadigitalsignalandperformingdigitalarithmetic.Whetheryou’rereusingoldercircuitblocksordesigningnewarchitecturesbasedonCMOSprocesses,you’lltakethesameapproachshownabovefordigitalCMOScircuitblocks,bothforfront-endcircuitdesignandphysicaldesign.ThevariousanalogcircuitblocksinCMOSVLSIgetconnectedintoalargersystemthateventuallygetsfabricatedfromasemiconductorwafer.Manydevicesthatappeartobeall-digitalareactuallymixed-signalsystemsandwillintegratesomeanalogcircuitblocksintothedesign.WhattoAnalyzeinCMOSVLSIDesignThereisplentytoanalyzeinCMOSVLSIdesign,bothbeforeandafteryoucreateaphysicallayout.Simulationsshouldbeperformedat3levelstounderstandelectricalbehaviorandeachrequiresadifferentsetofsimulations: Small-scalecircuitsimulations.Tasksliketransientanalysis,operatingpointanalysis,andfrequencysweeps(forlinearcomponents)willgiveyouthequantitativebehaviorofyourcircuitsinthetimeandfrequencydomains.Fornonlinearcomponents,operatingpointanalysisisespeciallyimportantfordesigningacircuittooperateinthelinearregime.  Large-scalecircuitsimulations.Oncelargercircuitblocksarecreated,you’llneedtorunlogicsimulations(fordigitalcircuits)orarangeofanalogsimulations.Theselarger-scalecircuitsimulationswillshowhowalargercircuitblockproducesoutputsforagivensetofinputs.Thisisanimportantpartofcircuitblockverificationbeforeintegratingmultipleblocksintoanentiresystem. System-levelsimulations.Resultsfromblock-levelsimulationscanbeusedinhigher-levelsystemsimulationstoshowhowgroupsofcircuitblocksinCMOSVLSIdesignwillfunction.Thistypeofsimulationtakesspecializedmodelingtoolsthatreducecircuitblocksintofunctionalblocks,whicharethenusedingraphicalsimulations.Manyprogramsforsystem-levelmodelingtakethisapproachandprovideagraphicalrepresentationofthesystem’sfunction(seebelow). System-levelmodelingforacomplexintegratedcircuit.Inacircuitsimulation,you’llneedtouseSPICEmodelsforyourcomponentstoperformnecessarysimulations,especiallyforMOSFETsusedinCMOSinverters.Thesecomponentmodelsarephenomenological;theyarenotintendedtosimulateCOTScomponents.Instead,thesecomponentmodelsaremeanttodescribetheelectricalbehaviorofdifferentcomponentsinyourcircuits,whichwilleventuallybesimulatedasanentiresystem.Beforeyougettothelevelwhereyouneedsystem-levelsimulationsinCMOSVLSIdesign,youneedtoolstodesignandanalyzeindividualcircuitblocksforyournextsystem.Thefront-enddesignfeaturesfromCadenceandthepowerfulPSpiceSimulatorpackagegiveyoueverythingyouneedtocreateanalog,digital,andmixed-signalCMOScircuitblocks.YoucanthenimportyourdesignsintoIClayouttoolstocreaterealcircuitblocks,andyoucansimulateanentirelayoutwithsystem-levelanalysistools.Ifyou’relookingtolearnmoreabouthowCadencehasthesolutionforyou,talktousandourteamofexperts.  LEARNMORE PreviousArticle ParametersforPCBLayout ThisarticleisaboutwhatsomeofthedifferentparametersforPCBlayoutareandwhytheyareimportantforcreatingaproductiveworkenvironment. 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