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use DC sweep variable to set another variable

Darrell L

I want to run a DC sweep in assembler with VPOS=0 to 3V.  I want to run this sweep with 3 cases of VNEG; VNEG=0, VNEG= -1V, and VNEG=-1*VPOS.  If I set the VNEG variable to '0 -1' it works as expected.  If I set the variable to -1*VPOS it works as expected and tracks VPOS.  But if I set the variable to '0 -1 -1*VPOS' it does not track VPOS in the sweep, it just uses a fixed level based on the default value of VPOS.

Is there a way to make all three cases together one sim setup?

Thanks,

Darrell

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  • Darrell,

    This is slightly tricky, because the normal behaviour is that variables used within an ADE sweep (i.e. in Explorer/Assembler rather than a native sweep such as the DC sweep) are evaluated prior to each point run. With simple variables, this evaluation doesn't happen (providing the expression is a legal expression) and gets passed to the simulator (which is what you want here).

    In this example, I set up VPOS to be swept in the DC analysis, and then defined three other variables as follows:

    The VNEG is set to be an expression of the others (and so is passed to the simulator, as can be seen in the input.scs below)

    parameters temperature=27 VPOS=1 VMULT=0 VCONST=0 VNEG=((VMULT * VPOS) + \
    VCONST)

    VMULT and VCONST are swept to be three different values, and then I've selected both and used Right Mouse→Group as Parametric Set (hence the orange colour), which means they are swept together. As a result, you have three sweep points which achieve what you want. You can see this in the graph below:

    Regards,

    Andrew

  • in reply to Andrew Beckett

    Thank you!  This solution is exactly what I needed.

    -Darrell

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