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    Shorted ground ports in Layout

    Hello.
    I faced some problem with ground ports. In layout I have ground plate (M9) , that has several ground ports. LVS sees all these ports as shorted. For inductors , I use metal resistor in order to separate port's conflict , but it is very difficult to use resistors for ground solid plate...
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  2. #2
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    Re: Shorted ground ports in Layout

    This (IME) depends on how the netlister and ERC respond to
    duplicate ports.

    One thing that has worked when multiple same-named ports
    are shorted for cause (by design) and the tool complains,
    is to take the port labels off all but one (replace w/ plain
    text, for documentation purposes).

    But check the ERC settings, you may be able to suppress
    shorts warnings (which, if thrown on features which are
    obviously the same net and the same port name, means
    the tool is not getting it) either globally or specifically

    Another option, if the tool comprehends resistance and
    does so using a marker polygon, is to impose trivial-L /
    trivial-R regions between the pad and the plane, and
    name the GND pads to (say) GND1, GND2, GND3... and
    let the netlist think the milliohms are on purpose (if you
    care about simulation, make the schematic represent
    the real pad-plane L, R). You might have to alter how
    you lay out the pads (like, relieve the corners and make
    current flow orthogonally outward from the pad only on
    the three sides, through three resistor-polygons in parallel,
    represented to suit).



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  3. #3
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    Re: Shorted ground ports in Layout

    If you use Assura, there should be an option which has been developed by PDK author to solve these kind of problems.



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    Re: Shorted ground ports in Layout

    I use Calibre.
    I try to use metal resistors , but it is very difficult with complicated polygons.



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    Re: Shorted ground ports in Layout

    Quote Originally Posted by Yakov_Yakov View Post
    I use Calibre.
    I try to use metal resistors , but it is very difficult with complicated polygons.
    There should be an option to hide ( or to fake ) these structures while LVS is running.



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  6. #6
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    Re: Shorted ground ports in Layout

    You do not have to use metal resistors or use different port names for multiple pads/ports on power/ground nets.

    In LVS, and/or in extraction, there should be a setting that would tell the tool/flow whether to short the ports with the same names, or keep them.
    For example, if your label for ports/pads is VSS, and you have many of them, the LVS would name them using unique suffixes, e.g. VSS_1, VSS_2, etc.

    For IR/EM analysis of power / ground nets, you should keep all pads/ports as unique, i.e. not shorting them (unless you can safely assume that the shorting will be done at the upper hierarchy levl, using low-resistive metals).



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