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TMDS181: Layout RULES and input lines length

Lenio Cacula
Genius 15900 points
Part Number: TMDS181

Should we make all the HDMI input (and output) traces the same length, or should those have different lengths based on the RULES of the Eval Board?

Thank you!

  

  • 0
    TI__Guru*** 140145 points

    Hi

    Is the TMDS181 being used on the source side or the sink side?

    On the source side, the HDMI spec calls for a skew of 0.2 * Tcharacter at TP1 (source connector).

    On the sink side, the HDMI spec calls for a skew of 0.2 * Tcharacter + 1.78 ns at TP2 (sink connector). For TMDS181 input, we can tolerate a skew of ~2 * Tcharacter.

    A Tcharacter is defined as the time duration of a single TMDS character equal to 10*Tbit.

    A Tbit is defined as the time duration of a single TMDS data bit.

    Please use the above skew number as a guideline for the trace inter-pair skew. But it does not mean the board should be designed to completely match these skew number. I would still recommend routing the trace length as close to each other as possible.

    Thanks

    David