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TMDS181 - Interfacing DP++ with TMDS181 output

Kawai
Guru 19785 points

Other Parts Discussed in Thread: TMDS181

Hello Team,

We are looking for a device which could bridge HDMI2.0 to DP++. Can we AC couple the TMDS181 output  ?.

I believe typical TMDS output is open drain circuit, so generally could not be used with AC coupling.

Our considering setup is the following,

HDMI connector ---------> TMDS181 ---------> FPGA DP++ input

Best Regards,

Kawai

  • 0
    TI__Mastermind 23815 points

    Hi Kawai-san,

    DP++ is a feature of GPU(Source) it is not a feature of Display(Sink).

    TMDS181 is an HDMI2.0 retimer, if you want to convert HDMI2.0 to DP you need a bridge, we don't have such devices.

    Regards

  • 0 in reply to Moises Garcia
    TI__Guru 60870 points

    Hi Kawai-san,


    As Moises noted, the TMDS181 cannot convert HDMI protocol to DP protocol.  The TMDS181 can, however, drive an AC coupled output, as long as there a pullups to 3.3V installed as well.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Guru 19785 points

    Hello Moises-san and JMMN-san,

    Thank you for your reply. First I had a wrong setup, required an AC coupling cap.

    Referring JMMN-san's answer, I believe TMDS181 TMDS output circuit is open drain circuit, am I correct ?
    i.e. without the pull up resistor at TMDS181 outputs, normal voltage swing level may not be able to pass through the AC coupling caps. I am thinking that with the following setup, correct TMDS181 output swing can be received at FPGA side with DC level cut.

    x                                                                 pull up with resistor
    x                                                                          |
    HDMI connector ---------> TMDS181 --------> C --------> FPGA

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Mastermind 23815 points
    Hi Kawai-san,

    This is right, you need pullup resistors where you depicted them in order to have HDMI AC coupled signals.
    However, if source is HDMI, your FPGA should have an HDMI receiver, not a DP receiver.

    Regards