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Is there more technical information available for the PCM4204?

Gerry Kurz
Intellectual 685 points
Other Parts Discussed in Thread: PCM4204, PCM4202

I have some PCM4204 parts where the VCOM output is not working correctly.


Could I get a block diagram of the reference circuit in the part?


Can I get a description of what the test pin does?

  • 0
    TI__Mastermind 27990 points
    Hi Gerry,

    All reference circuits are available in the EVM users guide here: www.ti.com/.../sbau104a.pdf
    or the Data sheet: www.ti.com/.../sbas327a.pdf.

    I do not have a full definition of what the Test pin does, it should be grounded as shown in the reference circuit and EVM.

    Justin
  • 0 in reply to Justin Bohr
    Intellectual 685 points
    Ok well then, do you have any idea of why the VCOM output would be acting the way it is? (please see the scope capture in the previous thread)

    I have tried grounding the test pin and it makes no difference.

    Who would know more about this part?

    I noticed that there is another thread about this issue and it was not resolved there either.
  • 0 in reply to Gerry Kurz
    TI__Mastermind 27990 points

    No we are not sure why this behavior is happening on VCOM, as we know it to be a resistor divider and should only be affected by the supply rail. The only limitation we know of is that it has a limited current output, and should have little to no current draw from it. It seems that this problem has popped up among a couple customers recently and we have not seen this issue from customers before.I have not been able to cause this issue on our EVMs (have tried both PCM4204 and PCM4202).

    The EVMs both have single buffer circuits being driven by each VCOM pin.

    I am discussing with the team to try and dig into this further.

    Justin

  • 0 in reply to Justin Bohr
    Intellectual 685 points

    Hi Justin,

    Thanks for the update.

    I am seeing this problem in 1 out of 4 parts, do you know if the other customers are seeing this problem in a similar percentage of parts?

    Could there be some correlation to a particular production run or batch of these parts?

    The batch code on my parts is 36C7TFT. Could you check the batch code on your EVM parts? Could you follow up with your other customers that have this issue and see what the batch code is on their parts?


    Best regards,

    Gerry

  • 0 in reply to Gerry Kurz
    Intellectual 685 points

    Here is some more screen shots of the problem. VCOM tracks 5V for about 800ms and then drops rapidly to 1V and then slowly decays to 0V.

    This happens with and without load and with the test pin grounded.

  • 0 in reply to Gerry Kurz
    Intellectual 685 points

    For some reason the screen shots did not appear in the last post. Here they are: