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TDP158RSBEVM: Could you kindly help to give some advice about the reason of noisy point?

Lian Wu
Genius 5250 points
Part Number: TDP158RSBEVM
Other Parts Discussed in Thread: TDP158, TMDS181, TMDS171

Dears:

We tested the Demo board, and found the image form HDMI OUT has some noisy point.

We changed the output's mode from DP-HDMI to HDMI-HDMI, and removed R26, R27, R31, R32, R33, R34, R35, R37, welded R9, R10, R11, R14, R15, R16, R17, R18.

We have test the HDMI Line, and there is no problem.

We can read the value of registers using scan tool, however, we can not get the eye diagram.

Could you kindly help to give some advice about the reason of noisy point?

And how can we get the eye diagram?

Btw, we use adapter form HDMI to DVI to connect display.

Many thanks 

Best regards

Luck Wu 

  • 0
    TI__Guru 60865 points
    Hi Luck,

    The TDP158 is intended for use as a source side AC-coupled TMDS redriver / level shifter. Using the double terminated HDMI input is possible for test / debug, but is not the intended use case. Also, the cable length between the source and the TDP158 will impact the performance.

    Eye Scan diagrams are only supported by devices in retimer mode, the TDP158 is a redriver only. You may want to consider the TMDS181 or TMDS171 for this application if it has a DC-coupled TMDS input.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Genius 5250 points
    Dear JMMN:
    Thanks for your reply, and could you kindly help to check our application.
    We only want to drive HDMI output(Souce) can connect with other HDMI input(sink) with cable of at least 20m.
    So we use TMDS181 is it OK? Since from datasheet we cannot find the length.

    Pls. give some advice about our choice of the application.
    Many thanks!

    Best regards
    Luck Wu
  • 0 in reply to Lian Wu
    TI__Guru 60865 points
    Hi Luck,

    Can you confirm if you plan to use the TMDS181 on the sink side or the source side? It sounds like the TMDS181 will be used on the source side of the cable. As long as the inputs to the TMDS181 are dc-coupled TMDS inputs that should be ok. It is difficult to specify max cable lengths because it varies greatly with cable gauge and quality. 20M is at the maximum range supported for HDMI 2.0 even with redriver /retimers.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Genius 5250 points
    Hi JMMN:
    How long is the maimum range supported for HDMI1.4b with redriver/retimer?
    And the other question is the DP159's drive capability better than TMDS181 or same with it under the same enviorment?
    Thanks a lot!

    Best regards
    Luck Wu
  • 0 in reply to Lian Wu
    TI__Guru 60865 points
    Hi Luck,

    The TMDS181 and the DP159 have the same driver capabilities. The maximum range for HDMI 1.4B with redriver / retimer is 20-25M.

    Regards,
    JMMN