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Trimming during MC runs and getting results

Mavrik

Hello Everyone,

I am new to Ocean script and i need some help in this regard.

I have the following problem.

  1. I have a Bandgap circuit in which i need to first run a MC simulation , with in that MC run 
    1. i need to first calculate the DC op point. (untrimmed Bandgap)
    2. Than i need to trim the band gap at room temp
    3. get the result out of trim code and apply it to the design variable.

Run MC over temperature again to get the Bandgap temperature variation

So my question is how to do it. i know i need a for loop but how do i get the results out and how it the flow or sequence of flow should be.

Any help would be great

regards

  • Also here is the script i am using  ocnWaveformTool( 'wavescan )

    simulator( 'spectre )

    design( "/localdisk/simulation/tb_bandgap_MC/spectre/schematic/netlist/netlist")

    resultsDir( "/localdisk/simulation/hessen/tb_bandgap_MC/spectre/schematic" )

    modelFile(

       '("active_thin.scs" "mc")

       '("active_thick.scs" "mc")

       '("active_hv.scs" "tt")

       '("diodes.scs" "typ")

       '("bipolars.scs" "typ")

       '("resistors.scs" "mc")

       '("capacitors.scs" "nom")

       '("wrapper.scs" "sigma3")

    )

    analysis('dc ?saveOppoint t  ?param "bgtrim"  ?start "-16"  

    ?stop "15"  ?step "1"  )

    desVar(  "bgtrim" 0 )

    desVar(  "ibias" 500n )

    desVar(  "avdd" 5.3 )

    option( 'temp  "25.0"

    )

    saveOption( 'save "all" )

    temp( 25.0 )

    for(N 1 2

    monteCarlo( ?numIters "1" ?startIter N

       ?analysisVariation 'processAndMismatch  ?sweptParam "None"

       ?sweptParamVals "27" ?saveData t

       ?nomRun nil ?append nil

       ?saveProcessParams t

    )

    monteExpr( "trimbg" "round(cross(VS(\"/vbg\") 1.2 1 \"either\" nil nil))" )

    monteRun()

    ;monteResults()

    monteSelectResults()

    ;vtrim=trimbg_25

    iterVsValue( "trimbg_25" )

    ;plot(getData("trimbg_25") )

    ;printf( "%d" "trimbg_25" ))

    ;ocnPrint( getData( "trimbg_25" ) )

    desVar("bgtrim" "trimbg_25")        here i am trying to assign the value but it seems it does not work

    ;delete('monteExpr)

    )

    monteResults()

  • You didn't mention which version of the tools you're using. The way Monte Carlo works is considerably different in IC61X compared with IC5141, so I might have suggested using some functions that I wrote in this solution. However, it might be simpler to just use ?saveData t in the monteCarlo call (which you are) and then after the monteRun you can do:

    vbg=value(round(cross(VS("/vbg") 1.2 1 "either" nil nil)) 'iteration N)  ; I think the sweep variable is called iteration

    You could try plotting the expression without the value() bit around it to see what the sweep variables are called. It's possible there are other sweep variables you'd need to do the value() over. I'm afraid I don't have time to try experiments in a variety of versions to cater for the various possibilities here.

    Then use:

    desVar("bgtrim" vbg)

    Regards,

    Andrew.

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