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 PSS analysis not converging for VCDL 

Last post Wed, Apr 24 2013 6:06 AM by Amessi. 6 replies.
Started by Amessi 24 Apr 2013 02:26 AM. Topic has 6 replies and 1196 views
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  • Wed, Apr 24 2013 2:26 AM

    • Amessi
    • Not Ranked
    • Joined on Wed, Apr 24 2013
    • Posts 4
    • Points 65
    PSS analysis not converging for VCDL Reply

    I am designing a VCDL for DLL. But the PSS analysis is not converging. I am trying to change "reltol" value but @ very begining of simulation it is showing a warning

    'reltol' is not a valid parameter for an instance of `pss' . Ignored

    Can anyone tell me if I can change reltol value at all in PSS analysis?

    • Post Points: 20
  • Wed, Apr 24 2013 2:33 AM

    Re: PSS analysis not converging for VCDL Reply

    reltol is an options parameter ("spectre -h options") not an analysis specific parameter. You can use errpreset to affect the reltol, but if you want to set reltol you'd do:

    myOpts options reltol=1e-5

    or similar.

    Andrew.

    • Post Points: 20
  • Wed, Apr 24 2013 2:56 AM

    • Amessi
    • Not Ranked
    • Joined on Wed, Apr 24 2013
    • Posts 4
    • Points 65
    Re: PSS analysis not converging for VCDL Reply

    Ya, its working. But I am not able to increase it from 1e-03(default value) though am able to decrease it....

    • Post Points: 20
  • Wed, Apr 24 2013 3:16 AM

    Re: PSS analysis not converging for VCDL Reply

    Setting errpreset=liberal on the PSS is as loose as we allow. It really doesn't make sense to loosen the tolerances too much with PSS as typically you want a reasonable dynamic range in whatever you're simulating with PSS. 

    Did you try that?

    Andrew 

    • Post Points: 20
  • Wed, Apr 24 2013 3:20 AM

    • Amessi
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    • Joined on Wed, Apr 24 2013
    • Posts 4
    • Points 65
    Re: PSS analysis not converging for VCDL Reply

    I am using

    method=gear2only

    lteratio=6(default=3.5)

    errprest=moderate 

    PSS is converging for 500MHz but fails in 800MHz 

    • Post Points: 20
  • Wed, Apr 24 2013 4:56 AM

    • HamidKhatibi
    • Top 200 Contributor
    • Joined on Thu, Jan 3 2013
    • Ithaca, NY
    • Posts 38
    • Points 580
    Re: PSS analysis not converging for VCDL Reply

     Hi Amessi

    May I ask you were do you set the above parameters, if you are using Cadence Virtuoso?

     Best

     

    • Post Points: 20
  • Wed, Apr 24 2013 6:06 AM

    • Amessi
    • Not Ranked
    • Joined on Wed, Apr 24 2013
    • Posts 4
    • Points 65
    Re: PSS analysis not converging for VCDL Reply

    It can be added in test bench manually

    • Post Points: 5
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Started by Amessi at 24 Apr 2013 02:26 AM. Topic has 6 replies.