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creating output expression while doing parametric sweep

Svilen64

Hi,

I am running a parametric sweep in Cadence Virtuoso and I want to create an expression that takes the difference of a voltage for the last parameter value and the first parameter value. How can I do that?
I want to create expression for that so that when the simulation is done that expression is calculated and gives me the difference. But then the question is can the simulator evaluate that expression without me going to the calculator. What I mean is that when it simulated the 1st parameter value spectre would not have yet the results for the last parameter value and then what will be the result of that expression?
Is it at all possible? And I would also like to do that for parametric sweep with Monte-Carlo.

I would rather not go do Ocean. I think this will complicate things too much.

Thanks
Svilen

  • Hi,

    assuming your parameter sweeps from minimum to maximum value, how about using leafValue() for this?

    I did not check if this really works, but you could try.

    Let VT("/signal") be the "voltage" you are talking about and "param" be your sweep parameter (actually a design variable) that you sweep from value a to value b.

    The first voltage of your sweep then is

    leafValue( VT("/signal") "param" a)

    the last voltage is

    leafValue( VT("/signal") "param" b)

    so the difference is

    leafValue( VT("/signal") "param" b)-leafValue( VT("/signal") "param" a)

    Here, you get a difference waveform, but that should work with a scalar value as well (like taken by "value(VT("/signal") timepoint)").

    For that to not evaluate for each point, you need to select the right EvalType (e.g. "sweeps" or "all")  or ignore the result for all values of param but the last one.

    The downside is, you still have to enter "a" and "b" manually into your output expression before starting the simulation.

    If you are interested in only min an max, then I guess

    a = ymin(VAR("param") ?overall t)

    b = ymax(VAR("param") ?overall t)

    can do the job for you:

    leafValue( VT("/signal") "param" ymax(VAR("param") ?overall t))-leafValue( VT("/signal") "param" ymin(VAR("param") ?overall t))

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