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About the spectre pss problem

kivvzhou

Hi, deal all:

     I use the old version of spectre (ver 5.10.41), when I do a vco  pss analysis , I found the spectre can't catch the frequency of  the vco. For example , before the pss analysis a run a tran analysis. measure the freq=1.4617G(when the vco have reach the stable state);but in the following pss analysis the freq=1.47119G; so the pnoise analysis result is not right. I don't know why the pss analysis can't catch the right frequency, and I have try nearly all the option setting, but no usefull.Can anybody tell me something about this ? 

 

  • Several points:

    1. I'd strongly recommend using something more recent than spectre from IC5141. The release is 5.5 years old, and spectre in that release has not been maintained for a long time.
    2. It's quite possible that the frequency that pss has found is the steady state, and that your transient is not long enough
    3. However, you may just need to tighten your tolerances. What do you have for errpreset, and reltol in particular? Try tightening reltol to see what happens (I would strongly recommend getting a newer spectre, e.g. from MMSIM72, first).

    Regards,

    Andrew.

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