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PSS convergence issue

apskohli

I'm having difficulties in achieving convergence in PSS simulation (corner dependent). This appears to be happening due to a few high impedance/tri-state nodes in the design getting capacitively coupled. Is there any way I can either loosen the tolerance or ignore these nodes for the simulation.

Also, can you please elaborate or provide an equation on how reltol, Iteratio and steadyratio are related.

Thanks,

Aman

  • Hi Andrew, Can you please help with this issue? Thanks Aman

  • Hi Aman,

    Sorry for the delay in replying - the day job has been getting in the way the last week or so! One of my other RF colleagues who often answers here has been on vacation too.

    You can't ignore nodes (that would be dangerous) and you can't loosen the tolerances for each node.

    Without knowing what your simulation settings are, it's hard to know what to suggest. Probably contacting customer support would be best because that way we can look at your data.

    For more info and the equation, launch `cds_root spectre`/tools/bin/cdnshelp (or cdnshelp from the MMSIM installation) and search for steadyratio. This will tell you in the PSS Shooting Convergence section how steadyratio works. In general nowadays I would leave it alone - don't set it yourself.

    Regards,

    Andrew.

  • In that case I'll take this up with Cadence support.

    Thanks!

    Aman

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