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PSS analysis not converging for VCDL

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?

Andrew Beckett over 12 years ago

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.
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Amessi over 12 years ago

Ya, its working. But I am not able to increase it from 1e-03(default value) though am able to decrease it....
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Andrew Beckett over 12 years ago

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
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Amessi over 12 years ago

I am using
method=gear2only
lteratio=6(default=3.5)
errprest=moderate
PSS is converging for 500MHz but fails in 800MHz
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HamidKhatibi over 12 years ago

Hi Amessi
May I ask you were do you set the above parameters, if you are using Cadence Virtuoso?
Best
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Amessi over 12 years ago

It can be added in test bench manually
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