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Captab parameter plotting across voltage

Eshar

Hello,

I am trying to generate a plot of one of the capacitance values generated by captab. My approach is as follows:

1. Use stimulusFile to include the instruction: Cap_dcInfo info what=captab detail=nodetonode sort=name threshold=0 where=logfile

2. Set up captab analysis: Analysis( 'dc ?captab t ?detail "nodetonode")

3. Run parameteric analysis across voltage to generate multiple cap. tables:

paramAnalysis( "vdd" ?start vstart ?stop vstop ?step vstep)

paramRun()

 

This seems to work when I only run step 2 and 3 meaning I see the multiple cap. tables in the spectre.out file. However, I am having trouble figuring out how to plot a specific capacitance value from the generated tables with the independent variable being "vdd". Although an example exists in a previous post http://www.cadence.com/forums/p/21764/1309486.aspx, it does not include the stimulus used and it did not attempt to plot multiple values but rather only print a single value.

 

Any help will be greatly appreciated. 

 

  • A better discussion would be to look at /forums/t/20426.aspx?PageIndex=2
    (although that's more to do with seeing it over time)

    You don't really need to use stimulusFile to turn on captab. Just do steps 2 and 3, and then if you do:

    selectResult('captab)
    outputs()

    you'll see all the available outputs. You can also access it from the results browser and then send to the calculator to find the right expression. For example:

    pv("out : net9" "Total" ?result 'captab)  ; don't need the ?result bit if you've used selectResult first

    The second arg for pv could be "Variable", "Fixed", or "Total". Because it was a parametric sweep, you'll see the capacitance value versus your swept variable.

    Andrew.

  • Thanks for the help. I didn't realize that 'captab was a result name. I thought that the circuit info had to be set in the stimulus file.

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