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Does the DS125DF410 support polarity inversion?

Casey Morrison
Intellectual 1985 points
Other Parts Discussed in Thread: DS125DF410, DS110DF410, DS110DF111, DS100DF410

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Question: Does the DS125DF410 support input and output polarity inversion?

Casey Morrison

  • 0
    TI__Intellectual 1985 points

    The DS125DF410 (like the DS100DF410, DS110DF410, DS124DF111, and DS110DF111) does support polarity inversion, or "PN swap." It accomplishes this by (optionally) inverting the polarity of the transmitted signal:

    • Channel register 0x1F[7]=0: normal polarity
    • Channel register 0x1F[7]=1: inverted polarity
    There is no polarity inversion on the input, per say, but this is unecessary as I will attempt to illustrate below. Consider the following four board layout scenarios:
    Signal routing on input of DS125DF410 Signal routing on output of DS125DF410 Recommended setting for register 0x1F[7] Comments
    Normal polarity, signals are not crossed Normal polarity, signals are not crossed 1'b0 No need to correct for any polarity inversion
    Normal polarity, signals are not crossed Inverted polarity, signals are crossed 1'b1 Invert the output polarity to preemptively correct for the PN swap on the output nets.
    Inverted polarity, signals are crossed Normal polarity, signals are not crossed 1'b1 Invert the output polarity to correct for the PN swap on the input nets.
    Inverted polarity, signals are crossed Inverted polarity, signals are crossed 1'b0 No need to correct for any polarity inversion. Both the input nets and output nets have PN swap, so the polarity is automatically corrected.
    Regards,
    Casey