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  Why Spectre noise-aware PLL simulation give huge PSF output and taking long time? 

Last post Fri, Sep 25 2009 4:45 PM by Tawna. 1 replies.
Started by bluestatic 18 Sep 2009 12:34 AM. Topic has 1 replies and 2367 views
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  • Fri, Sep 18 2009 12:34 AM

    • bluestatic
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    Why Spectre noise-aware PLL simulation give huge PSF output and taking long time? Reply

    we are trying to follow the spectre RF noise-aware PLL sim flow. Using MMSIM71 and IC5141_USR5(with latest hotfix), and the PLL is running at 2.5GHz.

    It goes well at the beginning, the divider ,CP and VCO model was extracted sucessfully, though we can not view it since the model was encrypted.  We don't see much problem since it is a general PLL structure and the flow is very straightfoward too.   BTW, We set the ChargPump load voltage (Vload) to 0.45~0.75.

    The transient simulation also goes well at first, untill the chargepump load voltage  gradually reached 0.45V, ie, the lower boundary of the voltage range that we set previously  in CP model extraction.  Now the simulation become very slow, the simulation step is in 0.01 fs. It takes 6 hours to simulate 3us.  And after the simulation run to 60us, the result psf data has become 65G bytes, which is not possible to be handled by wavescan.  Basides, my PLL will settle only after 100us. 

    For VCO CMI model, we set the "sampling point per second" to 50, and "inject jitter" to 100us. 

    Any clue any what's happening?  Please kindly help, thanks a lot. 

     

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  • Fri, Sep 25 2009 4:45 PM

    • Tawna
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    • Joined on Thu, Jul 10 2008
    • Snohomish, WA
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    Re: Why Spectre noise-aware PLL simulation give huge PSF output and taking long time? Reply

    Hi bluestatic,

    This question is probably best answered by submitting a Service Request via http://Sourcelink.cadence.com .  There could be multiple issues going on here.  

     With regards to Wavescan not being able to plot spectre tran results....

    Setting the environment variable

    setenv PSF_WRITE_CHUNK_MODE_ON true

    will allow IC5.1.41 to read native spectre files that are larger than 2G.

    For some of the history on this, you may want to look at these two http://Sourcelink.cadence.com solutions:
    11352482 Why did the default output change from psfbin to sst2 in transient analysis?
    11264780 MMSIM 6.X and higher does not break up large tran.tran files

    best regards,

    Tawna

    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 5
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Started by bluestatic at 18 Sep 2009 12:34 AM. Topic has 1 replies.