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Making a monte carlo simulation component specific

simbamford
Does anyone know how to specify that for a monte carlo mismatch simulation (presumably using spectre though I also have an ultrasim license), one or two specific transistors will not be subject to mismatch, i.e. will give nominal performance, whilst every other component will be subject to mismatch? Of course it would be convenient if this were possible through the virtuoso inferface, but any method would be useful.Any help gratefully received. 
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  • Andrew Beckett

    In ADE XL (assuming you're using IC61X; there's no UI support for doing what you want in IC5141), on the "Gear" icon next to the Monte Carlo Sampling cyclic choice (also available via Run->Monte Carlo Sampling in the pulldown), there's a button at the bottom of the form called "Specify Instances/Devices". If you bring this up it allows you to specify devices for mismatch - either as an inclusion or exclusion list. It's partly used to allow the mismatch to correlate between multiple tests which have different testbenches, but can also be used for the purpose you describe.

    The mmcflag parameter that Shawn describes must be specific to a particular PDK because it's not a parameter in spectre as far as I know (certainly not for bsim4 or bsim3v3; to be honest, the mismatch variation is handled outside of the model, so I can't see how it would be done in the device model. For a PDK they might choose to multiply the mismatch variations by this flag inside their subckt models, but as I said, that would be PDK-specific).

    Regards,

    Andrew.

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  • Andrew Beckett

    In ADE XL (assuming you're using IC61X; there's no UI support for doing what you want in IC5141), on the "Gear" icon next to the Monte Carlo Sampling cyclic choice (also available via Run->Monte Carlo Sampling in the pulldown), there's a button at the bottom of the form called "Specify Instances/Devices". If you bring this up it allows you to specify devices for mismatch - either as an inclusion or exclusion list. It's partly used to allow the mismatch to correlate between multiple tests which have different testbenches, but can also be used for the purpose you describe.

    The mmcflag parameter that Shawn describes must be specific to a particular PDK because it's not a parameter in spectre as far as I know (certainly not for bsim4 or bsim3v3; to be honest, the mismatch variation is handled outside of the model, so I can't see how it would be done in the device model. For a PDK they might choose to multiply the mismatch variations by this flag inside their subckt models, but as I said, that would be PDK-specific).

    Regards,

    Andrew.

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