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TMDS181: Device selection: TMDS181 vs SN65DP159 for HDMI SOURCE/SINK?

AnBer
Mastermind 28900 points
Part Number: TMDS181
Other Parts Discussed in Thread: SN65DP159,

Team,

I have see the below posts that discuss the TMDS181 and SN65DP159 use case:
https://e2e.ti.com/blogs_/b/analogwire/archive/2017/05/01/how-to-select-a-redriver-or-retimer-for-hdmi-2-0-jitter-cleansing
https://e2e.ti.com/blogs_/b/analogwire/archive/2016/09/27/how-to-select-the-right-retimer-for-hdmi-2-0-applications
The inputs seem to have a different coupling scheme (DC vs AC).

For an FPGA board with both an HDMI SRC and SINK like:
       HDMI IN CON -> TMDS181 (retimer) -> FPGA IN / FPGA OUT -> SN65DP159 (retimer/redriver)-> HDMI OUT CON
-Is there a way to use only one of the retimer/redriver in order to reduce the number of different devices on the board?
-For example is the below possible?
       HDMI IN CON -> SN65DP159 (retimer) -> FPGA IN / FPGA OUT -> SN65DP159 (retimer/redriver)-> HDMI OUT CON
Can the SN65DP159 coupling be adapted to be DC coupling to match the HDMI signaling?

Thanks in advance,

Anthony

  • 0
    TI__Expert 5455 points
    Hello AnBer

    The main thing that has to be clear is is the kind of signal that you would handle. HDMI use TMDS signals over it protocol, then you can have this signals AC coupled or DC coupled. HDMI is TMDS DC coupled, but some sources like FPGA's generate the TMDS signal but with a small DC level or AC coupled or these signals can be generated from a Display Port source. If those signals are Display Port, then will be AC coupled.
    TMDS181 is designed to handle with the HDMI signals, and it works like retimer and redriver. In case of DP159, it works like level shifter because you can have a source with Display Port dual mode signals or AC coupled TMDS (these signals have different levels than the HDMI signals), then with this device you can have in the output the correct voltage level for HDMI and additionally you have retimer and redriver characteristics that you can add to your signal.
    So, if you want to have an HDMI source and SINK I recommend you to use the TMDS181 on both sides, but it depends on the characteristics of the FPGA. if the FPGA output is actually TMDS AC coupled, you have to use the DP159 (like you say in your example).
    Let me know if this clarify a bit your understanding.
    Regards
    Francisco