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TPD12S016: HPD Signal powered by different power supply

Kenichiro
Mastermind 9165 points
Part Number: TPD12S016

[ TPD12S016 ] HPD Signal powered by different power supply

Hi Expert,

Can you help me to understand the HPD signal and HPD_B pin?

As my understanding, TPD12S016 has 5V_OUT pin for sourcing the HDMI power line and HPD signal is provided by sink device.
This means, there could be the possible scenario that the sink device is NOT powered by 5V_OUT (powered by their own supply).

In this case, in some cases that cannot meet the recommended conditions as below.
Is my understanding correct?



I'm not familiar with HDMI specification.
It's appreciated if this is the case or not.

Thanks,
Ken

  • 0
    Mastermind 9165 points

    I have studied the HDMI specification...

    There is a description as below for HPD.

    "Note that many Sink devices simply connect the HPD signal to the +5V Power signal through a 1000 ohm resistor. It may therefore be necessary for a Source to pull-down the HPD signal in order to reliably differentiate between a floating (disconnected) HPD and a high voltage level HPD signal. "

    This means that, even though the sink device is powered differently than 5V_OUT, in most case, HPD signal is divided by 1kohm and 10khom(internal pull down), then should be in the range specified in the datasheet.

    Please let me know, if you have different ideas.

    Thanks,
    Ken

  • 0 in reply to Kenichiro
    TI__Intellectual 1665 points

    Hi Ken,


    For the TPD12S016, it is assumed the HPD signal is supplied  by the 5V_OUT pin for the listed ratings. In the case it is powered externally as you mention, the voltage will still be 5V max to keep within HDMI specifications. Any higher HPD voltages will increase the likelihood of device failure and damage to the protected devices. I hope this helps!


    Very Respectfully,

    Brian Dempsey

  • 0 in reply to Brian Dempsey
    Mastermind 9165 points

    Hi Brian,

    Thank you for your response! Understood!

    Regards,
    Ken