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Differential Pairs Uncoupled Length

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  • Differential Pairs Uncoupled Length

    Hi. I am using Altium 20.1 and am doing the "Advanced PCB Layout" course. In lesson 4 discussing uncoupled length you purposely drag a net in a diff-pair, run DRC and show the violation. When I do it with the example files the violation does not appear. All diff-pair classes are defined.

    The only way to get it to work is to delete the pair and reroute it, create a violation and rerun DRC. Then it shows up.

    This is very worrisome because it means that imported designs from previous Altium versions create this situation and we don't see violations that are critical, of course, to the PCB design process. It means that the DRC is unreliable and this is a disaster.


  • #2
    More...When I rerouted HDMI_CLK then I could recreate a violation per above description. When I did the same for HDMI_D0 diff-pair I could not get Altium to detect the uncoupled length at all.


    • #3
      More..It is not consistent. Sometimes when I move a track in a diff-pair to create an uncoupled violation it shows and most time it does not.
      Attached Files


      • #4
        Double check setting in the diff pair rule - if you would like to see uncoupled length all the times, set in the rule "Max Uncoupled length" to 0

        Click image for larger version

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        • #5
          That's it, thanks.