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MOS area and perimeter are not calculated from parametrized w and l

joliveros

Hi all..

In my design I'm using nmos4 and pmos4 active devices from AMS DKIT 3.70 PRIMLIB library. As shown in the figure, when I try to edit their properties in Virtuoso Schematic, their area and perimeter fields are recalculated for w and l values (and are not editable for that reason). So, there is no problem when I assign numerical values to w and l, but when I parametrize those variables (to do parametric analysis with the Analog Environment or to pass symbols parameters down through design hierarchy with "pPar") the area and perimeter values are miscalculated. In fact, they are not recalculated, and the last calculated numerical values remain fixed regardless the actual value the parameters take. I guess this is really no a Cadence issue, but a DKIT one. However, I need to get around this inconvenient and I don't know how to do that.

Thanks in advance for your help.

Parents

  • Unfortunately this is one of the dangers of CDF callbacks that I describe in sourcelink solution 11223092. This happens all too often in PDKs - insufficient thought is made about how you parameterize things.

    A workaround would be to edit the CDF of the transistors (in the CIW Tools->CDF->Edit CDF, pick the component, and then look down for the fields for ad/as/pd/ps etc, and hit the "Edit" button in the parameters section. You can then make these parameters editable. If you don't have write access to the PDK, you can always make the change in the "Effective" CDF (rather than "Base"). 

    Having made the fields editable, you can replace the fixed numbers on the instances with edit properties, using pPar() with expressions (either based on the pPar() or using iPar() to reference the w and l).

    Regards,

    Andrew.

     

Reply

  • Unfortunately this is one of the dangers of CDF callbacks that I describe in sourcelink solution 11223092. This happens all too often in PDKs - insufficient thought is made about how you parameterize things.

    A workaround would be to edit the CDF of the transistors (in the CIW Tools->CDF->Edit CDF, pick the component, and then look down for the fields for ad/as/pd/ps etc, and hit the "Edit" button in the parameters section. You can then make these parameters editable. If you don't have write access to the PDK, you can always make the change in the "Effective" CDF (rather than "Base"). 

    Having made the fields editable, you can replace the fixed numbers on the instances with edit properties, using pPar() with expressions (either based on the pPar() or using iPar() to reference the w and l).

    Regards,

    Andrew.

     

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