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PCM4104: Soft Mute issue PCM4104

Giulio Montanari
Prodigy 30 points
Part Number: PCM4104

Tool/software:

I initialized the device in Software mode, but when trying to use PIN10 to mute the outputs, I don't get the usual smooth attenuation.


When entering mute, I get a sudden step.

When exiting mute, I do get the desired smoothed envelope.

Is this hybrid approach I'm trying to use — "Software mode" and "Standalone mode" — even possible?

How is it possible to achieve a damped behavior to avoid artifacts using the signal on PIN10?

  • 0
    TI__Mastermind 30791 points

    Hello,

    I assume you are using 5V supply , so  the differential output at full scale has to be about 6.15Vpp, but here your differential output is about 14V. 

    Can you confirm these outputs are correct, also please check VREF and VCOM pins and see if they are sitting at supply, GND and +2.5V respectively. 

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    Prodigy 30 points

    Sure! Here's the English translation of your message:

    Hello Arash,

    I confirm that the VDD pin (Pin 19) is powered at 3.3V, which supplies the digital section of the circuit. The analog section, including the VREF and VCC pins, is powered between GND and 5V.

    The maximum differential output at full scale is indeed 6.15Vpp as expected. However, the waveforms you observed were acquired after the buffer circuit, which has a gain of 2.545 V/V, so the output can reach approximately 15.65Vpp.

    To rule out other possible causes, we also performed measurements directly at the DAC output, obtaining results consistent with those observed after the buffer.

    I’m attaching an image showing the direct analog output of the DAC. Apologies if it appears slightly noisy, but it still clearly shows that the behavior is consistent.

    Let me know if you need any further information.

    Best regards,
    Giulio

  • +1 in reply to Giulio Montanari
    TI__Mastermind 30791 points

    Thanks for confirming the output of the DAC is 6.15VP-P. So everything seems to be okay with voltages of VCOM and Vref.

    In standalone mode,  the Mute triggers a soft-mute similar to that of the SW mute . However it doesn't explicitly say that in SW mode, the mute pin will act as soft or hard mute. I think  the MUTE pin  in SW mode act as a hard and quick mute to stop the output immediately ( as additional feature)  , otherwise the user should use the software to trigger a soft MUTE action. 

    I don't see any problem with using the mute in software mode except you would not get a soft mute at the insertion of MUTE.

    Regards,

    Arash