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PCM2900C - Drop-in replacement for the PCM2904?

Jason2015
Prodigy 80 points
Other Parts Discussed in Thread: PCM2904, PCM2900C, PCM2906C

Can someone please confirm that the PCM2900C is a drop-in replacement for the PCM2904?  We have used the PCM2904 in one of our products for years and just recently became aware of the documented "mic boost" / "digital gain" bug that it presents on some Windows Vista, 7, 8, and now Windows 10 systems.  We are hoping to simply replace the PCM2904 with the PCM2900C and move on.  Thank you.

  • 0
    TI__Guru* 95385 points

    Hi Jason,

    Welcome to E2E and thank you for your interest in our products!

    You can replace PCM2904 with PCM2900C, there should be no problem.
    One difference between these two parts is the descriptor for Max Power which is 100mA for PCM2900C and 500mA for PCM2904 but usually these parts consume around 60~80mA. So if there is no problem with the change in that descriptor this replacement should be fine.

    Best regards,
    Iván Salazar
    Texas Instruments

  • 0 in reply to Ivan Salazar
    Prodigy 80 points

    Thank you for the reply Ivan.  The Max Power spec is likely going to be a problem for us since our current product using the PCM2904 draws a total max current of around 140ma (we have other circuitry that is powered by the USB bus).

    Is there another version of the PCM2900C or another chip in the same line that is Windows 7 certified and has a higher Max Power Spec that we could simply drop in in place of the PCM2904?  If a pin for pin drop-in replacement isn't available, can you recommend a replacement with the Windows 7 certification of the PCM2900C but the higher Max Power spec of the PCM2904?

    Thank you again for taking the time to help with this.

    Regards,


    Jason

  • 0 in reply to Jason2015
    Prodigy 80 points
    Hopefully I'm replying correctly here... It looks to us like the PCM2906C would be a drop in replacement for the PCM2904, complete with Windows 7 certification and the 500ma Max Power spec. Is this correct? Thanks again!
  • 0 in reply to Jason2015
    TI__Guru* 95385 points
    Hi Jason,

    You can replace it with PCM2906C then. Its Max Power descriptor is 500mA.
    This one has S/PDIF digital port but you can just leaving it floating or connected to GND.
    Hope this help you.

    Regards,
    Iván Salazar
    Texas Instruments
  • 0 in reply to Jason2015
    TI__Guru* 95385 points
    That's right Jason,
    I think we just replied at the same time.

    Regards,
    Iván Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Prodigy 80 points
    Thank you for the quick reply Ivan. We'll get some of those here to test with ASAP. One last question since you mentioned it... We would not be using the S/PDIF digital port and would prefer to Ground it due to the RF environment that our product is used in. We have not had any time to look into this yet, so can you tell me if this port can be tied directly to Ground, or if should we do something else with it? Thank you again for your help.
  • 0 in reply to Jason2015
    Prodigy 80 points
    Hi again Ivan,

    While we are on the topic of the PCM2904 and PCM2906C, can you please tell me what the latest version of the PCM2904 chip is? I do not see any revision letter designator ("B", "C", etc.) for it yet most of the other PCM29xx chips have newer "C" versions. Thanks again.

    Regards,

    Jason
  • 0 in reply to Jason2015
    TI__Guru* 95385 points
    Hi Jason,

    Yes, the S/PDIF digital port can be grounded if not used.
    Regarding the part version, PCM290xC version it only includes PCM2900C/2C/3C/6C. The PCM2904 didn't upgrade considering that PCM2906C would include the same and more functionalities.

    Regards,
    Iván Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Prodigy 80 points
    Thank you again for your quick response Ivan. I see that the PCM2906C is certified for Windows 7, but there is no mention of Windows 8 or Windows 10 certification anywhere on the TI forums (at least not that I could find). Does Windows 7 certification apply to Windows 8.x and Windows 10, and if not, will TI be releasing a newer chip that is certified for these newer OS'? We would rather not change chips only to have to change again in the near future.
  • 0 in reply to Jason2015
    Prodigy 80 points

    Hi Ivan,

    I have one more question but this pertains to the PCM2904 chip that we are currently using.  With the Windows Vista/7/8/10 driver for the PCM2904 creating +30db of digital gain on the Mic input by default, would sliding the Level slider to 0db to remove the digital gain leave the incoming signal as it was originally (no affect on dynamic range, distortion, etc.)?  Thank you in advance for answering my questions.

    Regards,


    Jason

  • 0 in reply to Jason2015
    TI__Guru* 95385 points

    Hi Jason,

    I'm afraid that there is no certification yet for W8/8.1/10 but these devices work fine in that OS's.

    The additional gain problem is described in this application note. This was also a fix for the C revision parts.

    Regards,

    Iván Salazar

    Texas Instruments

  • 0 in reply to Ivan Salazar
    Prodigy 80 points

    Hi Ivan,

    Thank you for the answer on the certification and the link to the application note.  We had read that app note before but it didn't mention the slider.  Our own testing (as well as feedback from others that can be found online in TI forums and other sources) shows that moving the slider to 0db (or as close as possible) correctly removes the digital gain but we didn't see that specifically confirmed by TI anywhere so I thought I'd ask.  Anyway, thank you again for taking the time to answer all of my questions.  Your help is sincerely appreciated.  Have a great week!


    Regards,


    Jason