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 WARNING (CMI-2426) negative resistance in mimcap model 

Last post Fri, Oct 26 2012 12:54 PM by isazulkc. 2 replies.
Started by isazulkc 25 Oct 2012 09:19 AM. Topic has 2 replies and 972 views
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  • Thu, Oct 25 2012 9:19 AM

    • isazulkc
    • Top 200 Contributor
    • Joined on Thu, Nov 27 2008
    • Quebec, Quebec
    • Posts 40
    • Points 690
    WARNING (CMI-2426) negative resistance in mimcap model Reply

    Hi

    I got this warning when running a spectre (7.2) simulation on my design:

    " Warning from spectre in `mimcap':`I6.I1.C44', in `Cascode':`I6.I1', in `DiffAmp':`I6', during hierarchy flattening 

    WARNING (CMI-2426): I6.I1.C44.R0: `r' = -162.911 mOhm is negative. "

    any idea about what could cause "r" to be negative? Can this warning cause convergence problems or result in inaccurate results ?

    Regards,

     KC

    • Post Points: 20
  • Fri, Oct 26 2012 9:30 AM

    Re: WARNING (CMI-2426) negative resistance in mimcap model Reply

    You'd probably have to look into the mimcap model to see how the resistor value for R0 is computed. It's presumably a subckt model in your model files.

    Regards,

    Andrew.

    • Post Points: 20
  • Fri, Oct 26 2012 12:54 PM

    • isazulkc
    • Top 200 Contributor
    • Joined on Thu, Nov 27 2008
    • Quebec, Quebec
    • Posts 40
    • Points 690
    Re: WARNING (CMI-2426) negative resistance in mimcap model Reply

    Hi Andrew,

    Thanks for the reply, you right ! This negative resistance was due to maximum capacitance length . R0 become negative when the length in over 40um. Then I separate the mimcap into small ones (as it is done in the layout) to avoid this warning.

    Thanks again.

    Regards,

     KC 

    • Post Points: 5
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Started by isazulkc at 25 Oct 2012 09:19 AM. Topic has 2 replies.