Community Custom IC Design Warning (CMI-2477) Rds is less then 0.001 gpdk90nm

Stats

  • Locked Locked
  • Replies 2
  • Subscribers 125
  • Views 2382
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Warning (CMI-2477) Rds is less then 0.001 gpdk90nm

AL202409293035

Hi everyone! I am struggling with an issue of simulating circuits containing PMOS devices from gpdk90nm. Every time the simulation is initiated I get the following warning:

Warning from spectre during initial setup.
    WARNING (CMI-2477): M0: `Rds' = 867.631 nOhm is less than 0.001. Set to 0.


Global user options:
             reltol = 0.001
            vabstol = 1e-06
            iabstol = 1e-12
               temp = 27
               tnom = 27
             scalem = 1
              scale = 1
               gmin = 1e-12
             rforce = 1
           maxnotes = 5
           maxwarns = 5
             digits = 5
               cols = 80
             pivrel = 0.001
           sensfile = ../psf/sens.output
     checklimitdest = psf
               save = allpub

Interesting to note that this error only applies to PMOSes but not NMOSes and moreover - all the PMOS models from this library suffer from this issue. I do not think that the models are broken but rather the simulation setup is incorrect. Is there any obvious reason why this warning/error arises?

Thanks everyone in advance!

  • I did a quick check (I've not used gpdk090 for a while) and I can see this too. It's not a simulation setup issue as far as I can see - and the warning is nothing to worry about. 

    You can suppress the warning either by adding paramchk=0 to each of the models in the model file (this might be a bit cumbersome) or adding:

    warning_id=[CMI-2477] warning_limit=0

    to Simulation→Options→Analog, Miscellaneous tab, Additional arguments feed (at the bottom)

    I couldn't see any obvious reason why this is given for pmos devices and not nmos - I would expect the Rds values to be similar for both.

    Andrew

  • in reply to Andrew Beckett

    Thank you a lot, Andrew! You are a rock)

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.