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PSS shows inaccurate output results when no convergence reached

SteveRFIC

Hi,

I have another question on PSS simulator with hb engine.

I am simulating a circuit that settles after a certain time. If the circuit does not settle properly, for instance, ends up with an unwanted oscillation, then I expect the simulator to complain and will not converge.

In that case, if I use PSS with shooting engine and choose a certain tstab time, then PSS simulator fails to converge and will report simulation error and will not generate output data.

However, if I use PSS with hb engine and choose the same tstab time. simulation runs and gives a warning after it reaches the specified max. number of iterations, saying that it did not converge and the result may not be accurate. However, it still calculates the outputs data based on the last iteration results, which can be misleading, if I just look at the output data and not check the log file.

Is there a way to let the simulator stop when it did not reach convergence, showing sim error in the output fields, instead of showing inaccurate data?

I am using IC123_isr10 with mmsim151. I am not sure if this is related to just PSS with hb engine, or related to some generate spectre settings. Maybe this is just something specific to me, but I'd like to ask here to see if there is something can be done.

Thanks!

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  • Andrew Beckett

    This shouldn't happen. Does it happen if you use hb analysis rather than pss analysis with harmonic balance? Unfortunately I'd have to dig around for a good example to try to reproduce this myself, so if you're seeing this you should contact customer support.

    I know we made a change a few years ago to get hb to stop if it fails to converge (a while back it did indeed behave the way you describe, but that was changed a few releases before MMSIM151 - I think in MMSIM121 or 131). I assumed that would be the same with PSS with hb as well as using the hb analysis directly.

    Regards,

    Andrew.

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  • Andrew Beckett

    This shouldn't happen. Does it happen if you use hb analysis rather than pss analysis with harmonic balance? Unfortunately I'd have to dig around for a good example to try to reproduce this myself, so if you're seeing this you should contact customer support.

    I know we made a change a few years ago to get hb to stop if it fails to converge (a while back it did indeed behave the way you describe, but that was changed a few releases before MMSIM151 - I think in MMSIM121 or 131). I assumed that would be the same with PSS with hb as well as using the hb analysis directly.

    Regards,

    Andrew.

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