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Setting DC impedance for nets

Mysil B

We do quite a lot of designs where we use the trace resistance to balance diodes in parallel for DC currents. Is there any way we can set the a impedance constraint for this so we can control the lengths automatically? Since we vary the width on these traces and mix them with copper polygons, we cannot simply set a track length constraint... We'd need to have a constraint on total resistance from end to end on a single net.

Best regards, Mysil

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  • craigl

    You can create a custom constraint that calculates the resistance of the net and checks in constraint manager. There is a tutorial in Help->Documentation. Search for Advanced Constraint Tutorial.

    Craig

  • Mysil B
    in reply to craigl

    Well, I didn't get too far..

    The tutorial tells me to check these Formula boxes:

    But they seem to be missing from my version.. Is this feature not included in OrCAD PCB Professional?

  • redwire
    in reply to Mysil B

    I believe that requires the higher Allegro license and even within that it might require another option.  There is a feature matrix on Cadence and the VAR sites that shows what capabilities are enabled at each license level.

  • Mysil B
    in reply to redwire

    I see. We can generate a report listing the resistance in each net using NET_RESISTANCE. Is there any way we can access this variable using SKILL scripts?

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  • Mysil B
    in reply to redwire

    I see. We can generate a report listing the resistance in each net using NET_RESISTANCE. Is there any way we can access this variable using SKILL scripts?

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