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TMDS clock-detect of TMDS361B

yoshihiro hirata
Expert 1425 points
Other Parts Discussed in Thread: TMDS361B, TMDS341

Will output be oscillation when we don't use TMDS clock-detect of TMDS361B?

I think TMDS361B  input don't have fail-safe circuit, also TMDS341.
I referred to TMDS341 datasheet page 18.
If it is mistake, please correct my thinking.

<TMDS341 datasheet page 18>
TMDS input pins do not incorporate fail-safe circuits. An unused input channel can be externally biased to
prevent output oscillation. One pin can be left open with the other grounded through a 1-kW resistor as shown in
Figure 31.

Best regards,
Y. Hirata

  • 0
    TI__Mastermind 23815 points

    Hi Yoshihiro,

    If you don't use clock detect feature, and you have a very noisy environment you may have some signals in the outputs.

    TMDS361B is an improved version of TMDS341,that's why the fail-safe circuit is implemented as a clock detect feature.

    Could you please elaborate why you would disable the clock detect feature?

    Regards

  • 0 in reply to Moises Garcia
    Expert 1425 points

    Quote-san,

    Thank you for your replay.

    Our system is receiver system with TMDS361B.
    Souse system (ex: PC) monitor is not only HDP(Hot Pllug Detect) but also TMDS signal level to judge connected Souse system and Receiver system.

    If it uses Clock-detect function of TMDS361B;
    Souce system judges disconnect when HDMI cable inserts connector.
    Because 50 ohm of input pulled up resister integrated TMDS361B is open before souse system clock provided.
    Souce system couldn't catch High level clocks.
    Therefore we couldn't use clock-detect.
    Please let me your advice.Thank you.

    Best regards,
    Y.Hirata

  • 0 in reply to yoshihiro hirata
    TI__Mastermind 23815 points

    Hi Yoshihiro,

    The recommended fail-safe configuration for TMDS341 is when no port is used.

    If you are going to use the port but is currently unplugged, just leave it as is.

    If your environment is very noisy there would be some noisy in the output.

    Regards