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 Assert checks for overvoltage with duty-cycle 

Last post Wed, Aug 26 2009 9:50 AM by MarkSummers. 7 replies.
Started by MarkSummers 18 Aug 2009 07:44 AM. Topic has 7 replies and 2477 views
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  • Tue, Aug 18 2009 7:44 AM

    • MarkSummers
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    Assert checks for overvoltage with duty-cycle Reply

    We use assert to check for device overvoltage.  Due to overshoot in the circuits, we have to either increase the limits for VGS, VGD, VDS, etc, or use a duration setting to prevent false errors due to overshoot.  What we should really check is the duty-cycle of the overvoltage level.  A random example would be if a VGS signal exceeds 2V more than 5% then issue an error.  The window of time to consider could be set in the assert statement, or better over the simulation time.  Is this possible to do.  I do not know of a way to do this.  Any help would be appreciated.

     

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  • Wed, Aug 26 2009 8:00 AM

    • MarkSummers
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    Re: Assert checks for overvoltage with duty-cycle Reply

     I beleive I have found a method to do this.  If I use the following expression, it seems to work.

    avg_check1 assert mod=nch  expr = "avg((abs(V(g,s)) > 2.0) )" level=error max=0.01 message="Signal Overvoltage too high" 

     However this does not generate an error in the ADE violations display.  It shows up in the spectre log, but not violations display.

     The following check does end up in the ADE violations display

    avg_check2 assert mod=nch  expr = "(abs(V(g,s)) > 2.0) " level=warning  message="Signal Overvoltage too high" 

    The difference is one is evaluated during the tran simulation and one is evaluated after the sim is over.  Is there a setting to allow assertions calculated at the end of the analysis toend up in the ADE violations display?

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  • Wed, Aug 26 2009 8:06 AM

    • aplumb
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    Re: Assert checks for overvoltage with duty-cycle Reply
    In the 'Simulation - Options - Analog' form, 'Check' tab, do you have 'checklimitdest' set to either 'psf' or 'both'?

    Andrew.
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  • Wed, Aug 26 2009 9:23 AM

    • MarkSummers
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    Re: Assert checks for overvoltage with duty-cycle Reply

     I had it set to psf.  I changed it to both, but with the same result

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  • Wed, Aug 26 2009 9:26 AM

    • aplumb
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    Re: Assert checks for overvoltage with duty-cycle Reply
    Which version of MMSIM are you using for Spectre and IC5/6 for ADE?

    Andrew.
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  • Wed, Aug 26 2009 9:30 AM

    • MarkSummers
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    Re: Assert checks for overvoltage with duty-cycle Reply

     mmsim7.1.84  icfb5.1.4

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  • Wed, Aug 26 2009 9:42 AM

    • aplumb
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    Re: Assert checks for overvoltage with duty-cycle Reply
    What does 'icfb -W' return for sub-version?

    I've been out of the IC5141-related R&D loop for too long so someone Cadence-internal will have to pick it up from here

    Works well in IC6.1.3! ;-)

    Andrew.
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  • Wed, Aug 26 2009 9:50 AM

    • MarkSummers
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    Re: Assert checks for overvoltage with duty-cycle Reply

     icfb-5.1.41_isr500.6.133

    • Post Points: 5
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Started by MarkSummers at 18 Aug 2009 07:44 AM. Topic has 7 replies.