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TMDS181: TMDS181 Review

John DeCesare
Intellectual 280 points
Part Number: TMDS181

Hi,

I'm designing in the TMDS181 as an HDMI sink and I was wondering if my schematic can be reviewed and the following questions answered:

  1. I have the DDC I2C pulled to 5V on the connector side.  The SCL_SNK/SDA_SINK go to 3.3V pins on the FPGA and are pulled up to 3.3V on the FPGA side.  Will the 5V pass through the device and present 5V on the SNK sides?
  2. What should I connect the CEC pin on the HDMI connector?
  3. Do I need AC coupling caps between the TMDS181 and the FPGA?

Thanks!

John7651.TMDS181.pdf

  • 0
    TI__Guru**** 156181 points

    Hi, John

    Please see my review feedback. 

    7651.TMDS181_TI_Reviewed_10062022.pdf

    1. I have the DDC I2C pulled to 5V on the connector side.  The SCL_SNK/SDA_SINK go to 3.3V pins on the FPGA and are pulled up to 3.3V on the FPGA side.  Will the 5V pass through the device and present 5V on the SNK sides?
      1. No. 5V will not leak to the other side. But you may have to implement TMDS181 DDC snooping option as not all HDMI sources support clock stretching on the DDC bus. 
    2. What should I connect the CEC pin on the HDMI connector?
      1. You can pull it up to 3.3V through a 27k resistor if not used. 
    3. Do I need AC coupling caps between the TMDS181 and the FPGA?
      1. Depend on FPGA input requirement. If implementing AC coupling caps between TMDS181 and the FPGA, then you would need external 50ohm termination to 3.3V.

    Thanks

    David