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PCM1690: PCM1690 click when I2S data stops

Jack Oclee-Brown
Prodigy 10 points
Part Number: PCM1690

Tool/software:

Hello,

Please can I have some advice on PCM1690. In our implementation we are finding that PCM1690 emits a small click when the I2S data is halted (BCK, LRCK & DIN1-4 stopped, SCKI still running). I've attached a picture below that shows captures of the I2S data and also the output showing the click.

PCM1690 is configured in HW mode. fs=48kHz, SCKI=512fs.

To avoid this click we have tried several things:

1. Our DSP allows us to keep BCLK running continuously. We have tried this but there is no change in the click.

2. We have tried applying I2C soft mute before stopping I2S data, but the click is still present.

3. We have tried pulling AMUTEI pin low before stopping I2S data, but we find that the click from AMUTEI mute is worse than the LRCLK stopping click (see data below).

  • 0
    TI__Mastermind 24720 points

    Hi

    Can you confirm the output voltages when MUTE is asserted? note that  " an AMUTEI low input causes the DAC output to cut-off from the digital input and forces it to the center level (0.5 VCC1)." Can you please send an input to one of the channels and  provide the output snapshot just before and after mute is inserted ( similar to the second plot you have) for both VOUTP and VOUTM of the channel that input is applied to. I like to confirm that both  outputs are correct before the MUTE insertion and they  go to 0.5 VCC after MUTE.

    Regarding the soft mute , datasheet explains that by setting MUTDA[8:1] = 0, the attenuator is increased to the last attenuation level in the same manner as it is for decreasing levels. This configuration reduces pop and zipper noise during muting of the DAC output. So the soft mute should only help .

    Also I need a zoom in screenshot to check the edges of I2S signals wrt each other to verify the format ( similar to Figure 31 in datasheet). What is your BCK rate? 

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    Prodigy 10 points

    Hi Arash,

    Thanks for the quick reply. Understood, I will capture some more data for your study. Here is a zoom in screenshot showing the I2S data. BCLK = 64fs = 3072 kHz

  • 0 in reply to Jack Oclee-Brown
    TI__Mastermind 24720 points

    Sure, send them when you have them ready.

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    Prodigy 10 points

    Hi Arshan,

    I have some data for you. I captured this directly at VOUT1+ and VOUT1-.... it's quite noisy so hopefully you can make sense of it.

    1kHz sine playing, muted by pulling AMUTI low. DC coupling used on the scope. Scope traces are offset -2.5V.

    1kHz tone during steady state

    DIN1 = 0 , BCLK, LRCLK and SCKI running. AMUTEI pulled low in the middle of the trace (reasonably loud click)

    DIN1 = 0 , BCLK, LRCLK and SCKI running.BCLK and LRCLK stopped in the middle of the trace (click is about 6dB less than AMUTEI click but still audible)

  • 0 in reply to Jack Oclee-Brown
    TI__Mastermind 24720 points

    Hi, I will take a look at it today and let you know.

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    TI__Mastermind 24720 points

    Hello Jack,

    I looked at the plots, it is different from your first set of plots of VOUTP/VOUTM.

    Whenever there is an interruption to I2S, there will be a pop or click and it is a know fact. With the soft mute,  it attempts to reduce the pop noise. The mute should happen before the interruption of I2S and I am not sure were your MUTE was wrt to I2S in the plots you sent. 

    If you are using a AC coupling, once the device is stopped or muted, there is still energy on the cap and that can cause the pop you hear.

    If you are using an amp after the DAC, the amplifier has to be muted ( or disabled)  as well, before DAC is muted. 

    These devices are not pop free so it is expected to get a pop or click when there is discontinuity at the output for whatever reason.

    Regards,

    Arash