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TAS5756 random digital noise

Other Parts Discussed in Thread: TAS5756M

Dear TI Community,

I'm facing with a problem using TAS5756M.

Sometimes, at power on, in a random manner, after I2C initialization and speaker mute activation, I can ear a digital noise coming out from the loudspeakers, whose intensity changes by temperature variation. This means that if I make the TAS5756M colder by "dry ice" spray, the noise greatly reduces, but it comes out again soon as the temperature rise up again.

The MAX temperature reached is not so high and it is about 74”C on  the body of the TAS.

I have  used a heat sink, but the random noise is still present.

I tried to use ldo regulators for the AVDD and DVDD with better noise performance (like the TI LP2989AIM-3.3) but it doesn't solve the problem.

The AVDD and the DVDD are generated by a low noise ldo regulator starting from an input voltage of about 12V ( this is a clean analog voltage used for the audio path).

The PVDD is derived  from the output of an ac/dc wall adapter (24V 2.5A) 

 

Maybe someone has experienced the same problem and can suggest improvements in order to avoid the random  digital noise.

If it is possible I would like to revise the schematic with some TI application engineer, but I don't know how to do.

 

Thank you very much in advance for your help and cooperation.

 

Best Regards,

 

Diego Ferraiuolo

  • Where can I post the schematic in order some TI expert can review it?

    Tanks in advance.
    Diego Ferraiuolo
  • Hi Diego,

    Have you tried using our EVM + PPCMB with your 24V AC/DC wall supply? I would recommend doing so. Also I would recommend referencing following schematics for your power supply design and application circuits:

    http://www.ti.com/lit/pdf/slou366

    http://www.ti.com/lit/pdf/slau583

    You can post your schematic to this e2e using the attachment icon.

  • Hi Damian, 

    thanks for your reply!

    >Have you tried using our EVM + PPCMB with your 24V AC/DC wall supply?

    Yes, I have used my 24V AC/DC wall supply with TI EVM + PPCMB. It seems to be OK 

    even if I didn't try to turn on and off the EVM some consecutive times.

    >Also I would recommend referencing following schematics for your power supply design and application circuits:

    >http://www.ti.com/lit/pdf/slou366

    <http://www.ti.com/lit/pdf/slau583

    Yes, I tried to follow the reference schematics; the power supply design is different because of the different application. The AVDD and the DVDD

    are generated by a low noise, low dropout regulator starting from an input voltage of +12V (this is a clean analog voltage for the audio path).

    Today I have faced with a particular issue. 

    The default setup of my design is the following:

    - gain mode 26dBV

    - switching frequency mode 8 x Fsync where Fsync is 96 since my sample rate is 48 KHz.

    I have changed the switchig frequency to 6 x Fsync instead of 8 x Fsync changing the values of the resistors that set the gain and the switching frequency.

    I have noticed, with this new setting, that the noise coming out from the loudspeakers was very loud, even if it was a white noise.

    Moreover, when I play the piano notes I can ear distortion from the  loudspeakers, that is , changing the switching frequency, I have greatly amplified

    the original problem.

    Have you some suggestion? Maybe this can help to solve the problem.

    Should it be related to the output filter?

    Thanks in advance for your help and support.

    Best Regards,

    Diego Ferraiuolo.SCHEMATIC _ TAS5756M.pdf

  • Hi everybody!

    I'm afraid my question  will be

    lost at the bottom of the post.

    Could someone revise the attached schematic, please?

    Best Regards;

    Diego Ferraiuolo