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Original question:

TMDS171: ON OFF operation of power

TMDS171: ON OFF operation of power

K.Hamamoto
Guru 12155 points
Part Number: TMDS171

Hi

I have an another question about Power on Sequence.
At Fig 23, it is shown the power up sequence.

On the other hand, at the customer's board,OE pin voltage is start up to very slowly. (Please see the following waveform.)

Is this acceptable for as the correct power up sequence?

At the customer's board , this device may be into Standbymode when the power up is as above. (The TMDS signal is not output.)

What the register we should confirm whether this device is in standbymode or not?

We are considering why the TMDS output is not output when the power up sequence is as above.

Best Regards,

Koji Hamamoto

  • 0
    TI__Guru**** 177506 points
    Koji-san

    The TMDS171 supports several methods of power management. It can enter power down mode using three methods; (1) HPD is low; (2) Writing an 1 to register 09h[3]; or (3) de-asserting OE.

    Have you checked HPD and see if it is high or low?

    If you shorted the OE ramp time, do you then have the video output?

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 12155 points

    Hi

    Thank you for your reply.

    >Have you checked HPD and see if it is high or low?

      Yes. The voltage of this pin(#33: HPD_SNK) is 3.3V at abnormal operation such as above. And #4 pin(HPD_SRC) voltage is 3.3V as well.

    >If you shorted the OE ramp time, do you then have the video output?

       They will check.

    On the other hand,the some of register value was different at normal operation and abnormal operation.

    OK: 1Ah=46
    1Bh=08
    1Eh=08

    NG; 1Ah=46
    1Bh=0A
    1Eh=0A

    And this phenomenon is appeared 1 sample of 3 samples.(means 1 board of 3 boards)

    Best Regards,

    Koji Hamamoto

  • 0 in reply to K.Hamamoto
    TI__Guru**** 177506 points
    Koji-san

    0x1Bh and 0x1Eh are BERT error counter, are they sending the data while the OE is still ramping up?

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 12155 points
    Hi David-san,

    It is maybe "Yes".
    They are using a cable such as include data line and power line. So that , the voltage and the signal is provided immediately when the cable is plugged in to the board.

    Is this kind of usage not acceptable for this device?
    Or is there any concerns?

    Best Regards,
    Koji Hamamoto
  • 0 in reply to K.Hamamoto
    TI__Guru**** 177506 points
    Koji-san

    If the source is sending the data while OE is still ramping up, this can be an issue since TMDS171 is still in power down mode. So they need to make sure TMDS171 is in normal mode before doing the link training.

    Thanks
    David