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TAS5825M: Cannot clear over current fault

Robert Seliger
Prodigy 95 points
Part Number: TAS5825M

Questions

My question is, other than a short circuit (which is not the case here), what can cause a TAS5825M to lock-up with an over current fault that cannot be cleared even after cycling the power?

My follow-up question is what can be done to clear an over current fault that otherwise refuses to go away?

Details

We are using a TAS5825M on a board we developed. For now our processor is a Raspberry Pi. Our board provides the I2S clocks. The sample clock rate is 48KHz. The Pi is configured so that it does not generate the clocks. It took us a while but we have a stable ALSA configuration that enables us to use commands such as 'aplay' to playback WAV files and 'mpg123' to playback MPG files. We can play back 44.1KHz and 48KHz files.

We have a speaker connected to the TAS5825M left channel. We have a 10K resistor instead of a speaker on the right channel. We have configured the TAS5825M to mix L+R for both channels.

Recently we installed an open-source program that enables streaming to the Pi via Apple's airplay protocol.  The program is called shairport-sync. Our clocks produce a 48KHz sample rate, but shairport-sync can only playback at 44.1KHz. To accommodate this we configured an ALSA plugin to do the necessary conversion. It took us a while to sort things out, but we finally got shairport-sync to playback without any errors being reported. However, there was no sound. When we then used 'play' we still did not get any sound. Something "broke".

We inspected the TAS5825M registers and found register that register 0X70 was reporting 0x02, which means left channel over current fault. We tried clearing the fault using register 0x78 but that did not work. We were able to clear the fault using register 0x01, but as soon as we executed 'aplay' the fault reappeared. Of course we did things like cycle the power, but that did not work either. Eventually we unsoldered the chip and replaced with a new chip. The new chip worked as long as we did not use shairport-sync and the ALSA conversion plugin.

Any help you can provide would be most appreciated.

Respectfully,

Robert Seliger

WHIM LLC

  • 0
    TI__Genius 9995 points
    Hi Robert,

    OC fault can be cleared by power down cycle:
    w 98 00 00
    w 98 7f 00
    w 98 01 11

    Or you can pull low PDN to achieve this. My colleague Andy will follow up this issue for you.

    Regards,
    Alix Wan.
  • 0 in reply to Alix Wan
    Prodigy 95 points
    I set the registers as described above and it does clear the OC fault. However, as soon as I execute 'play' the fault returns. It would seem that we somehow broke the chip (see my original posting). We cannot figure out how this could have happened.

    So I am back to my original question, which is what can cause a sustained over-current fault other than a short circuit?
  • 0 in reply to Robert Seliger
    Prodigy 95 points
    Still hoping to get an answer to my question.
  • 0 in reply to Robert Seliger
    TI__Expert 6295 points
    can you give one block diagram to explain what you did on " shairport-sync and the ALSA conversion plugin"?

    regards
    Linda
  • 0 in reply to Xiaolin Qin
    Prodigy 95 points
    I can send you the specific configuration files for ALSA and shairport-sync. Can you provide an email address?

    Since I first posted, we do have a configuration that enables shairport-sync and aplay to work with the TAS5825. The issue is that while we were developing the configuration we managed to damage two TAS5825s. We don't understand how we could have damaged the chips.

    The only thing we were trying to sort out were the conversion of shairport-sync's default sample rate of 44.1KHz and default word size of 16 bits to a sample rate of 48KHz and a word size of 32 bits. This is where the ALSA plugin comes in. We did not write any code for this. We only tried various ALSA configurations that pertain to sample rate and word size until we found settings that work. This is what I will send you via email.
  • 0 in reply to Robert Seliger
    TI__Guru 52115 points
    Hi Robert,

    If you don't use the open-source program you mentioned and just use the tool 'aplay' to play WAV files, you can see the OC fault, correct?

    Also, could you show me your schematic?

    In addition, how did you get the TAS5825M configurations? In your driver code, do you download TAS5825M configurations while I2S clocks are stable and running?

    Andy
  • 0 in reply to Robert Seliger
    TI__Guru 52115 points
    Hi Robert,

    Have you solved this issue yet? I assume you probably have figured out why by yourself. Let us know if you still need help from us.

    Andy