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TMDS171 application conditions

Rocson He
Intellectual 1830 points

Other Parts Discussed in Thread: TMDS171

Hi team,

I have automotive customer that's making one Hub project, that would have one HDMI input port, and there is a device /MAX9293 transmitting the HDMI signal to GMSL output interface.

The HDMI cable from other peripherals connecting to this Hub/HDMI, is unknown yet. And the Hub PCB size is around 75mm *75mm.

So we are thinking if one HDMI retimer like TMDS171 would need to be added.

Could you help share more the application conditions HDMI retimer is required, like cable length, data rate, etc ?

Does HDMI qualification test also need adding retimer to pass?

Thanks.

  • 0
    TI__Mastermind 23815 points
    Hi Rocson,

    You may need a redriver/retimer depending on signal integrity. There is no one recommendation for all cases.
    When cable, or PCB traces are too long, signals is attenuated, so you need a redriver to recover the signal amplitude.
    The attenuation of the cable or PCB trace will depend on length and material, if you know the loss profile of the material it would be very useful.

    Besides signal attenuation you have to deal with skew and jitter, this is injected from mismatches in traces and noisy environment.
    Jitter and skew becomes more important in higher data rates, this is where you need a retimer.

    You are not compelled to add a redriver/retime to pass HDMI qualification, you need to meet the parameters in specification, sometimes is necessary to add redriver/retime to meet specification.
    TMDS171 is a redriver/retimer that switches functional mode depending on data rate, if you place it your design will be more robust.

    Regards