simulators in affirma

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    Simulators in the Affirma Analog Design Environment

    Sachin Shinde

    Xiaolai He

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    • Cadence design framework II environment

    consists of many Cadence tools which are

    interoperale without re!uiring data conversion"• D#II is an open system allowing the user to

    integrate third party tools like simulators using

    programmale netlister or enter their own design

    data"

     Simulators

      Direct Simulators

      Eg" Spectre

      Socket Simulators

    Eg" SpectreS$ cdsSpice

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    Direct Simulation %s Socket

    Simulation• Direct Simulation

     & 'his is a preferred method ecause uses the new features addedto Spectre simulator and uses direct simulation"

     & (ith direct simulation$ the netlist uses the synta) of the simulator

    w*o any processing to evaluate e)pressions" & 'he netlist is a direct reflection of the design"

    • Socket Simulation & 'he netlist is processed y Cadence S+ICE to evaluate all

    e)pressions and resolve passed parameters"

     & Socket methodology is used to integrate a simulator if the currentsimulator cannot handle e)pressions or parameters passing"

     & Efficient operation in various interactive mode such as simulationstop and restart or change values and resimulate"

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    ,ore Aout Direct Simulation

    • Important -enefits of Direct Simulation

     & Improved performance in netlisting"

     & Improved performance of simulation for

    Spectre"

     & .eadale netlists"

     & .ead only design can e simulated provided

    that they are e)tracted" & Improved support of standalone netlisting"

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    /ther Simulators

    • In addition to Cadence S+ICE and Spectrecircuit simulator popular analog andmicrowave simulators can e used through

    a set of integrated simulation interfaces" & Eg" ,eta Software0s HS+ICE circuit simulator$

    H+0s ,1S microwave simulator$ CompactSoftware0s Harmonica microwave simulator"

    • (e have A##I.,A HS+ICE interfaceinstalled on our system"

    • (e do not have a HS+ICE simulator

    installed yet"

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    Spice$ +Spice and HSpice

    • S+ICE was originally developed at theElectronics .esearch 2aoratory of the3niversity of California$ -erkeley 456789

    • +Spice is a +C version of S+ICE4,icroSim Corp"9

    • HSpice is a version 4Avant:"9 that runs on

    31IX workstations and larger computers"'his is particularly fast version and onethat should e normally used"

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    Spectre Simulator 

    •  A##I.,A Spectre simulates analog and digitalcircuits at the differential e!uation level"

    • 'he capailities of Spectre circuit simulator aresimilar in function and application to S+ICE$ utSpectre is not descended from S+ICE"

    • Spectre and S+ICE use the same asicalgorithms eg" 1ewton .aphson$ direct matri)solution$ ut every algorithm is newly

    implemented"• ,anual claims Spectre algorithms are the est

    currently availale and is faster$ accurate$ morereliale and more fle)ile than previous S+ICE

    like simulators"

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    Improvements of Spectre over

    S+ICE• Improved Capacity

    • Can simulate larger circuit"

    • Improved Accuracy• Improved component models and core simulator algorithms

    • Improved Speed

    • Improved .eliaility• Improved ,odels•  Analog HD2S

    • (orks with Spectre HD2 and %erilog; A

    • .# Capailities•  Analyses of ,i)er$ oscillators$ sample hold and switched;capacitor filter

    • ,i)ed Signal Simulation• Spectre circuit simulator coupled with the %erilog;X2 simulator in the A##I.,A

    environment can simulate mi)ed analog and digital circuit

    • Environment• #ully integrated into Cadence D#II for A##I.,A and also in Cadence Analog

    workench design system

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    S+ICE compatiility of Spectre

    • S+ICE is a industry standard language withmany variations of S+ICE synta) on markettoday"

    • Each vendor modifies it with different capailitiesand*or slightly different synta)"

    • #or convince of S+ICE users A##I.,A Spectresimulator provides S+ICE .eader as an

    e)tension to its native language that acceptsmost variations of S+ICE input"

    • S+ICE .eader supports S+ICE

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    Cadence S+ICE

    • Cadence S+ICE simulator is an interactivecircuit simulator ased on 3C -erkley0sS+ICE< program"

    • ,odified architecture for interactiveoperations plus enhancement thatautomatically improve convergence with

    prolem circuit"• Can e used within the Analog simulation

    environment or as a standalone simulator"

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    Cadence D#II Architecture

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    HS+ICE Simulator 

    • >old standard for accurate circuit simulation"• E)tensive set of uild in devices$ models including models for small

    geometry ,/S#E' and ,ES#E'"• Compatile with Spice and ,SI1> input format"• Cadence supports a lirary of primitives and a full interface of

    HSpice"• High +erformance?

    • HS+ICE achieves upto

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    Inverter E)ample

    • Compared performance of Spectre$

    SpectreS$ cdsSpice and HS+ICE

    simulators using the inverter e)ample"

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     A,I@1 ,odels in Spectre and

    HspiceSpectre 4A,I@19 Hspice 4A,I@19

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    Simulation with SpectreS

    • 3sed the spectre,/S models forsimulation in thenominal mode"

    • Does not simulateusing the hspicemodels"

    • 'otal time re!uired forthe

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    Simulation with cdsSpice

    • Can e simulated

    using either the

    Hspice or Spectre

    models for simulationin the nominal mode"

    •  'otal time re!uired

    for the

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    Simulation with HS+ICE

    • 3sing the A##I.,A

    hspice interface could

    generate the netlist

    fro HS+ICE"• Couldn not simulate it

    cause do not HS+ICE

    simulator is not

    installed"

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    1CS30s Spectre and Hspice

    Comparison• 'he process? 'S,C @"

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    Conclusion

    • ,any variations of S+ICE simulators are availale in themarket each optimied for different function"

    • 'he choice of a type of S+ICE simulator is very prolemdependent"

    • Spectre availale in A##I.,A is not a S+ICE simulator"• Spectre is well documented"

    • Cadence S+ICE is the S+ICE simulator availale in A##I.,A which can e used with cdsS+ICE or

    SpectreS interface"• In the inverter simulation we found spectre simulator to

    e much faster than SpectreS and cdsSpice"

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    Conclusion 4cont"9

    • CouldnFt compare the speed of simulation forSpectra and Hspice simulators"

    • 1CS3 tutorial states that they didn0t find andsignificant difference etween HS+ICE andSpectre simulations results"

    • In general we would recommend the use ofSpectra over SpectreS and cdsSpice if thedevelopment environment is Cadence"

    • If portaility of design across differentenvironment is desired a Spice ased simulatorlike Hspice or cdsSpice is recommended"

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    .eferences

    •  Affirma Analog Circuit Design Environment

    3ser >uide$ Cadence$ +roduct version

    ""$ April