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 beginner question for monte carlo analysis in ADE XL 6.1.5. 

Last post Mon, Apr 22 2013 7:20 AM by apple419. 2 replies.
Started by apple419 19 Apr 2013 03:13 PM. Topic has 2 replies and 1127 views
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  • Fri, Apr 19 2013 3:13 PM

    • apple419
    • Top 500 Contributor
    • Joined on Fri, Apr 19 2013
    • Norristown, PA
    • Posts 35
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    beginner question for monte carlo analysis in ADE XL 6.1.5. Reply

    Hi everyone,

       Previously I used PSPICE for my analog/mixed-signal simulations. Recently I tried to convert my design to Cadence Virtuoso-Spectre. I have been self-studying it for a few days. It is quite different from PSPICE and it looks like powerful and complicated. Due to lack of training materials I have to google online or look at the HEP manual installed with the software.

      Here I have a simple question regarding monte carlo analysis using ADE XL. Here is my procesure:

    1) Capture design (a inverter) in schematic editor. Then from there, launch -- ADE L

    2) In ADE L, I setup the simulator, library, variables, output, and analysis. I can run simulations (tran, DC) successfully.

    3) next I want to do a monte carlo analysis.  I know I have to start ADE XL for the monte carlo analysis. Basically I want to see how the model parameter (VTO) variation changes the circuit performance. In my technology library folder, I noticed there is a mc folder along with other folders (tm, ws, wp, wz, wo). I guess this mc folder is used in the monte carlo analysis. 

       My question is how do I use the models in the mc folder to specify lot variation and device mismatch variation?

       In PSPICE it is very straight forward. I just put dev and lot statement after the parameter I want to vary then it is ok to go. But how to do it in ADE XL environment? 

        Is there any detailed tutorial available somewhere in this forum? 

    Thanks for your help! 

    • Post Points: 20
  • Sun, Apr 21 2013 9:00 PM

    Re: beginner question for monte carlo analysis in ADE XL 6.1.5. Reply

    Hi Apple419,

    Spectre requires 'statistics' block to be defined in the model files. This 'statistics' block further consists of 'process' and 'mismatch' blocks etc. where you define the parameters statistical distributions.

    Please refer to Monte Carlo Analysis in Analyses Chapter of Spectre User Guide for more details. You may specifically refer to "Specifying Parameter Distributions Using Statistics Blocks" section to understand it in more details.

    Regarding how to run Monte Carlo Analysis in ADEXL you may refer to Chapter - 'Performing Monte Carlo Analysis'.

    For now I am not aware if there is any direct reference available for mapping Pspice Monte Carlo Analysis to Spectre Monte Carlo Analysis.

     

    With Regards,

    Ashish

     

     

    • Post Points: 20
  • Mon, Apr 22 2013 7:20 AM

    • apple419
    • Top 500 Contributor
    • Joined on Fri, Apr 19 2013
    • Norristown, PA
    • Posts 35
    • Points 550
    Re: beginner question for monte carlo analysis in ADE XL 6.1.5. Reply
    Hi Ashish Patni,

    Thanks for your help. During the weekend I studied more about doing monte carlo analysis in Spectre and I did some research on some documents regarding MC analysis found from our foundry website. Finally I got the monte carlo simulation work.

    The way Cadence Spectre does monte carlo analysis is different from PSPICE. In PSPICE one needs to figure out the process and mismatch variations by himself by looking at the technology process spec (for LOT, or process) and the transistor area in your design (for DEV, or matching). Then modify the transistor models accordingly. 

    In Spectre, as you mentioned, a special model file has to be prepared for this purpose and Spectre calculates the process and mismatch automatically based on this file and the sigma you specified and the transistor size on the schematic. Our foundry has already provided the model file for monte carlo in Spectre. I just need to point to this model file and specify the section and input the sigma value. Then I am able to run Monte Carlo analysis and see plots after that.
     
    Thanks again! 
     
     Apple419
    • Post Points: 5
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Started by apple419 at 19 Apr 2013 03:13 PM. Topic has 2 replies.