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XO simulation using HB/PSS method. Linear IC Fail

ChrisMc

Hi everyone,

I hope that some of you give me a solution to fix my issue.

I simulate my XO (32MHz, pierce topology) in HB, using the application note:

www.cadence.com/.../new-mmsim-12-1-harmonic-balance-features-auto-tstab-and-auto-harmonics.aspx

My issue is that sometime,(with the same Test bench and same artiste stat and settings) the linear IC fail to find out the initial frequency.
The result is that the final frequency is right but the magnitude is wrong. I'd compare with transient simulation (much longer), and when the IC linear works, the magnitude is right.

the rror message is the following:
"INFO: Can't find linear initial value. Using twotier Newton"

I'm using cds6:

IC: 615ISR15

SW: v09

MMSI: 111

I've the same trouble for jitter simulation with PSS. And my jitter is pretty bad because the SNR is low.

How can I do to remove the issue everytime ? because I don't know the reason.

Thanks in advance for your help.
Chris

 

  • Hi Chris,

    Well, the blog was about MMSIM12.1 and you're using MMSIM11.1 (so an older version), although that may not be the issue - it's hard to tell without seeing either your analysis setup (the bottom part of the input.scs file) or your spectre output log. Can you post both? (ideally give it a try using MMSIM12.1 using the auto modes that Tawna describes in her blog too).

    I don't know what "SW: v09" is, either, by the way.

    Regards,

    Andrew.

  •  Hi Andrew,

    Yes i know that my version is older than this used in application note the field are the same.
    The support has fix my issue. It seems that my error came from the initial condition which I set for the simulation. I'v removed it and know It works well.

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