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instances based simulation tolerance setting

DavidLou

hello experts,

we are playing Spectre simulator with very high precision circuits so naturally we need very tight tolerance setting, e.g., 'reltol 1e-6 'vabstol 1e-8 'iabstol 1e-14. on the other side, the translated digital signals or testbench signals not necessary to work for this hard at all. with the simulation running, it's easily run into convergence problem due to this unnecessory tight digital signals or testbench signals.

so wonder if I can set design dependent tolerance so that the real critical analog circuit works with tight tolerance, but not anything else?

thanks,

David

  • Andrew Beckett

    Hi David,

    First of all, it's fairly unusual to need that level of accuracy setting - even with high precision circuits. So I would recommend talking to a Cadence application engineer to analyse if it's really necessary.

    However, it is possible to control the accuracy for different subckts or instances using How to set different reltol settings for different instances or subcircuits when running with Spectre

    There's no UI for doing this in ADE currently - you have to use the Additional Parameters field on the Miscellaneous tab in Simulation->Options->Analog in ADE and type in the parameters.

    Regards,

    Andrew.

  • DavidLou
    in reply to Andrew Beckett

    Thanks Andrew,

    I don't have account to access the support yet (need CAD help). But I do find a few clues from Spectre User manual like "tran param" to sweeping parameters during transient analysis, and MTS options. hope that's what you  are suggesting similar methods. 

    thanks

    David

  • Andrew Beckett
    in reply to DavidLou

    Hi David,

    Unfortunately it's not yet documented in the main documentation - the only current place is that support article (there's a CCR to get the documentation fixed). It's not the dynamic parameters (tran param) or MTS options that are used here. At the moment we want to track usage of this feature via the support portal, so I don't think I can really advertise the precise mechanism here.

    Regards,

    Andrew.

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