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Differential pair length matching (Red colour error)

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  • Differential pair length matching (Red colour error)

    Hello

    i have started routing my DDR3 for the first time with the guidance advanced pcb layout course and now i am blocked with some of the unknown solutions

    i have started my preliminary length matching for the data signals for the bank 0 everything is going fine at the begining and then the preliminary length matching for the differential pairs it is always showing red colour error on the PCB tool bar i have set the rule for length matching data bank0 matched net length with the tolerance of 10 mils for the single ended signals and 5 mils for the differential paris

    i dont able to understand why is the red colour marking on the differential pairs is there is any error? or what should i do for rectify this error what is the reason behind this

    i cant able to find a way to do the length matching for the differential pair in order to maintain the proper impedance i have to maintain the width gap of 0.15 mm but with this specification it is difficult to do the length matching for differential pairs

    any one could please suggest me how to solve this error and how you achieve proper length matching for differential pairs with proper isolation between the tracks

    Any ideas or suggestions would be greatly helpful

    please see the attached picture that i have did length matching on the DDR 3 clock signal when i checked the length it is perfect but the real problem is there is not proper isolation between the both waves in order to achieve 100 ohm impedance

    Thank you
    prabhu
    Attached Files
    Last edited by prabhu; 02-26-2018, 09:04 AM.

  • #2
    Can you attach screenshots of the rules which you set up and also the "red bar" screenshot?

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    • #3
      Hello Robert thank you so much for your reply actually i have resolved my error i came to know there is red colour only for differential pair routing because i have set 0.127 mm tolerance and positive and negative signal are not on their same length so that's why i have had those errors

      In my previous attached documents if you see in the picture there is any extra length attached to the wave in order to make the same length for the differential pair signal but we did not respect the gap width between two signal will not be same will there be any consequences? because i have saw in your video you explained for the differential pair signaling we can add length to match the signal legnth

      for the DDR3

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      • #4
        The "bumps" are not ideal for impedance (you are right, we do not respect the gap between tracks), but if there is no other way ... we just need to do it. The "bumps" should be kept to minimum and if possible, you should try to avoid them.

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        • #5
          Hello Robert thank you so much for your kind reply inorder to do the length matching i am not able to do the proper signa

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