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TAS5721: TAS5721 - no audio

Wojciech Mitus
Prodigy 90 points
Part Number: TAS5721
Other Parts Discussed in Thread: PCM5102

Hello, i am working on the prototype board with TAS5721. I have proper communication with TAS over I2C - i am able to initialize the chip and exit shutdown, but i get no audio on amplifier's output.

Here are some facts to help debugging the issue:

 - board is built according to "2.1 system" application note from TAS5721 data sheet

 - the chip gets all the necessary supplies (AVDD 3.3V, DVDD 3.3V, PVDD 13V)

 - to initialize the chip, i am using sequence suggested previously by Shawn Zeng:

X1B 00 ! Factory trim
X21 00 00 42 03 ! Set SubChannel Mixer to (L+R)/2 
X05 84 !Exit Shutdown and configure the device in 2.1 Mode
X07 30 !Set MAster Volume to 0dB

Additionally, i'm setting I2S word length to 16 bit, by writing value 0x03 to register 0x04.

- after exiting shutdown, i get 376Khz PWM on all of the OUTx pins, but duty cycle is constant 50% (despite I2S data coming into chip) and thus no signal variation can be seen after lowpass filter.

- i have checked data input pins of the chip with oscilloscope, and it seems like TAS is getting proper data on input: SCK is 1.41Mhz, LRCK is 44.1Khz, and SDIN is looking like it's feeding some data into chip

- from SCK/LRCK values, i infer that audio format is 44.1Khz I2S with 16 bit word length. I am able to get proper audio from this feed when connecting another board with PCM5102 chip configured for I2S format.

- i don't have MCLK signal (MCLK is pulled low)

- error status register 0x02 stays 0x00 all the time 

Is there some additional initialization/setting that i'm missing? What to check next?

Thanks,

WM

  • 0
    TI__Mastermind 24835 points
    Hi WM,
    TAS5721 need MCLK input to make the internal DSP work. If there is no MCLK input, it's expected that no audio output is on the AMP output.
    Does the front-end ADC/Codec has MCLK output signal? If not, you have to use 32-bit/44.1kHz I2S format, and use the I2S SCLK signal for both SCLK and MCLK input on AMP.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 90 points
    Hi Shawn, thanks, i misunderstood a statement i a data sheet:

    "The clock section uses MCLK or the internal oscillator clock (when MCLK is unstable, out of range, or absent) to produce the
    internal clock (DCLK) running at 512 times the PWM switching frequency."

    As i understand, above is not enough for the TAS5721 to work properly.

    As my front-end does not easily provide MCLK, i have routed BCLK to MCLK and increased BCLK to 64 x fs, and now i'm getting sound output, but there is another problem: when i connect 8 ohm speaker to one of the channel outputs, and do a reset/initialization sequence (while I2S is feeding audio to the chip), amplifier plays sound by one second and shuts down. Oscilloscope shows that PWM on OUTx pins is stopped. I have to do reset/reinit again to get one second of sound again, and then amp shuts down almost every time. I was able to get it playing longer few times, but that's about it. When speaker is not connected, oscilloscope shows audio signal after lowpass filter, and amp is not shutting down.
    So it seems like it's shutting down under the load of 8 ohm speaker (?) Error register 0x02 stays 0x00 all the time, even after PWM shutdown by TAS.

    Regards,
    WM
  • 0 in reply to Wojciech Mitus
    TI__Mastermind 24835 points

    Hi WM,

    Please check the PVDD voltage, is it stably within the recommended operating range? Looks like it's a UV fault.

    Best regards,

    Shawn Zheng

  • 0 in reply to Shawn Zheng
    Prodigy 90 points

    Hi Shawn, you were right. I have used PSU which was to weak for the entire system. After switching to better PSU, everything is working as expected.

    Many thanks,

    WM

  • 0 in reply to Wojciech Mitus
    TI__Mastermind 24835 points

    Hi WM,

    Gald to hear that you make it work well! Please feel free to creat a new post in the forum if you have any other question.

    Best regards,

    Shawn Zheng