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Standard Deviation Summary in Monte Carlo Simulations Across Multiple Corners

alho1

The tool versions are below:

Virtuoso IC 6.1.8-64b.500.33
Spectre 23.1.0.063 64bit

Hello,

When performing a Monte Carlo simulation, the Yield tab shows a standard deviation in the results.

If the simulation is performed with several corners (not parameters), the question is which standard deviation value is used for the summary output. Each corner has its own standard deviation.

Is the worst-case standard deviation used for the summary? If so, why is it sometimes the larger and sometimes the smaller value?

At 100% yield it seems to always be the larger value (worst case), but at 0% yield it is sometimes the larger and sometimes the smaller value.

Does anyone know how this value is determined?

Thanks very much for your reply!

Alexander

Parents
  • Andrew Beckett

    Alexander,

    According to this: Inconsistency in value of Standard Deviation across Yield View tab and Summary View in Assembler, Explorer and ADE XL it should be the "worst case" standard deviation, but what that might mean is the standard deviation of the corner with the worst mean (and the spec might affect which direction that is). Not sure - I'll see if my colleague in product engineering who covers this knows.

    Regards,

    Andrew

Reply
  • Andrew Beckett

    Alexander,

    According to this: Inconsistency in value of Standard Deviation across Yield View tab and Summary View in Assembler, Explorer and ADE XL it should be the "worst case" standard deviation, but what that might mean is the standard deviation of the corner with the worst mean (and the spec might affect which direction that is). Not sure - I'll see if my colleague in product engineering who covers this knows.

    Regards,

    Andrew

Children
  • Andrew Beckett
    in reply to Andrew Beckett

    Alexander,

    In newer versions, there's now a tooltip explaining that it's the standard deviation of the worst corner. However, what is not clear is how it determines which is the worst corner (especially if there are no specs). I'm trying to find that out.

    Andrew

  • alho1
    in reply to Andrew Beckett

    Hi Andrew,

    thanks for looking into this.

    Regards,

    Alexander

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