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Impedance signal recommendations

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  • Impedance signal recommendations

    Hello Robert and Everyone,

    The attached image shows IMX6 recommended impedances for various signal groups but these are not used in the actual IMX6 Rex board. The Rex board uses 55, 90, and 100 ohms but these the datasheet recommends 50 for single ended, 85 for PCIE, 90 for USB and 100 for all other diff signals. Can you clarify this? Can I just use 50 for single ended and 100 for all diff traces?

    Click image for larger version

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  • #2
    - We had stackup for 55, so I used it. Usually you will find information, that single ended digital signals can be routed 50-55OHM impedance. You can use 50.
    - I would follow differential pair impedance as recommended in design guide. If you are sure it is going to work, you can put PCIE and USB on 90OHMs (sometimes I do it), but I would not use 100 instead of 85.