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PCM5102A: 10% of PCBAs with PCM5102A can not play the audio with sample rate of 22.04KHz

MZ Liu
Prodigy 60 points
Part Number: PCM5102A
Other Parts Discussed in Thread: PCM1754, PCM1780

The audio DAC PCM5102A is used on our PCBA to play audio. The audio to be played have 2 types of sample Rates: 22.05KHz and 24KHz
Now we have one problem: During the PCBA mass production, 10% of the PCBA boards can not play the audio with 22.05KHz sample rate. While it can play 24KHz sample rate audio normally.

On our PCBA, the PCM5102A is designed with following configuration:

  • 3-wire I2S slave, which means that BCK, DIN and LRCK signals come from the I2S master (MCU act as I2S master on our design).
  • PCM5102A's system clock input (SCK) signal connects to GND through one 10Kohm pull-down resistor. It means that it means that we choose "Clock Slave Mode with BCK PLL to Generate Internal Clocks (3-Wire PCM)". Neither LRCK = 32 * Fs (sample rate) nor LRCK = 64 * Fs (sample rate) can play the 22.05KHz sample rate audio.
  • PCM5102A's FMT signal also connects to GND through one 10Kohm pull-down resistor, which means the audio data format is configured to be I2S Audio Data Format.
  • PCM5102A's XSMT signal connects with VDD (3.3V) directly.

As the failure rate is actually very high, Please give a quick and strong support. Thanks.

  • 0
    TI__Guru 53973 points

    Hi Mouzheng,

    What is the exact behavior of "cannot play the audio"? Is there zero output? Or is there some output but is distorted?

    1. I suspect your problem is rooted in that the PCM5102A does not support either 22.05kHz or 24kHz audio in 3-wire mode.  In 3-wire mode, the PCM tries to detect the input clock frequency and configure the device automatically.  It will attempt to use settings for detectable ranges.  When you use a rate that is un-supported, the device usually just autoconfigures for the nearest supported frequency, but that is not guaranteed.  Generally, I see when customers use 22.05kHz or 24kHz, the device auto configures to the 32kHz configuration.  

    I do not recommend you use BCK=32×FS, only BCK = 64×FS.

    In addition, the device requires that the BCK signal be continuous.  And by that we mean that the there are no interruptions in the clock.  Some I2S sources will use a higher frequency BCK, but then gate the output after 32 bits.  

    Assuming you are using a continuous bit clock, you could try connecting SCK = BCK.  This would put the device in 4-wire mode, and which usually allows the device to operate even if it cannot determine the LRCK frequency./

  • 0 in reply to Paul_Frost
    Prodigy 60 points

    Hi Paul,

    Thanks for your feedback.

    "What is the exact behavior of "cannot play the audio"? Is there zero output? Or is there some output but is distorted?" Of the 10% issue PCBA, most boards has no output (zero output), a few has seriously distorted output.

    From your feedback, does it mean that PCM5012A does not support either 22.05KHz or 24KHz sample rate audio, right? Of all the already mass production PCBA, we found that the PCBA can play 24KHz sample rate even with BCK = 32 x Fs, of course from your suggestion, BCK = 64 x Fs will be better.

    In our design, the PCBA only plays the audio when required but not always. When the PCBA plays one audio file, the BCK signal will be continuous during playing the audio.

    "You could try connecting SCK = BCK.  This would put the device in 4-wire mode, and which usually allows the device to operate even if it cannot determine the LRCK frequency." If you confirm that the device PCM5102A can play audio even if it cannot determine the LRCK frequency when connect SCK signal and BCK signal together, I will update the design in this way. Anyway, I will have a try based on this suggestion. 

    Thanks a lot.

  • 0 in reply to MZ Liu
    TI__Guru 53973 points

    Hi Mouzheng,

    I recommend that you try the SCK=BCK test on some of your failing units.  It might be a work-around.  Is it possible for you to change your sampling rate? Switching to a supported rate, like 48kHz, would be the best solution.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 60 points

    Hi Paul,

    Thanks, I will try with the SCK = BCK.

    I already had the idea to change the sample rate of the audio. But the audio file to play is standard audio file of our company. So it's not easy to change it.

    Except the SCK=BCK and changing the sample rate, Is there any other device with I2S interface only (additional I2C or SPI interface is not needed ) that support both 22.05KHz and 24KHz?

    Thanks.

  • 0 in reply to MZ Liu
    TI__Guru 53973 points

    We have some devices that could support that sample rate in 4-wire mode, but I recommend the SCK be a higher order clock than 64×fS for those (including the PCM51xxA).  If you have some higher order clock in the system, i.e. 256×fS, then these devices can work without I2C or SPI configuration.  Possible devices would be the PCM1780/81, PCM510xA, PCM1754.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 60 points

    Thanks for your support.

    Checked the datasheet of PCM1780/81 and PCM1754

    Below picture is copied from the PCM1780/81 datasheet.

    Below picture is copied from datasheet of PCM1754

    22.05KHz and 24KHz are not found in the datasheet of PCM1780/81 or PCM1754. Here want to check with you whether PCM1780/81 and/or PCM1754 supports 22.05KHz and 24KHz or not. If not, then any other devices without I2C or SPI may support 22.05KHz and 24KHz?

    Thanks.

  • 0 in reply to MZ Liu
    Prodigy 60 points

    Hi Paul, Today I have a try to connect the SCK and BCK signal together, unfortunately, the PCBA board does not play the audio at all.

    The PCM5102A is used on our PCBA board for the audio DAC. and 3-wire I2S is used for the audio interface. and BCK = 22.05KHz or 24KHz on our board as some audio files' sample rate is 22.05KHz and some audio file's sample rate is 24KHz.

     Here I want to double check with you, that based on the above configuration, connect the SCK and BCK together can play the audio files (including 22.05KHz and 24KHz)?  If not, any other work-around solutions?

    Look forward your feedback and your great support.

  • 0 in reply to MZ Liu
    TI__Guru 53973 points

    Hi MZ,

    1. Both the PCM175x and PCM178x can support 22.05kHz and 24kHz in a four-wire configuration with a valid SCK multiplier (256xfS, for example).

    2. Let's go back to basics on the PCM510xA board before we commit to this being an issue with the sample rate.  Let's check the following on one or more of the failing boards:

    a. Can you share your schematic for review?

    b. When your clock signals are applied in the 3-wire configuration, what is the voltage on the VNEG pin? What is the voltage on the LDOO pin?

    c. Do you measure a valid voltage on all supply pins? VDD, DVDD, CPVDD?

    d. If you connect an external I2S source (might need to wire to the board) and play a supported sample rate (e.g. 48kHz), does the DAC now work?

    I would like to eliminate other possibilities before we come to a conclusion, as I would still expect the PCM510xA to have some functionality at 22kHz, just somewhat limited performance.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 200 points

    Hi Paul

    • For those 90% that passed 22.05kHz test in production line. Is it guaranteed to work in the market?

  • 0 in reply to user6325641
    TI__Guru 53973 points

    Hi,

    I cannot guarantee that they will work in the field.  This could be dependent on temperature, supply voltage, or other variables that might shift over time.  It is possible that some of the devices are only marginally auto-detecting the clock inputs, so if some other factors in the system shift, they could stop detecting.

    Thanks,

    Paul