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Question of the TAS5731 THD+N vs Frequency

Wayne Chen (Audio AE)
Genius 15950 points
Other Parts Discussed in Thread: TAS5731M, TAS5731

Hi Sirs,

Would you pls advise how to make flat THD+N vs Frequency plot with the TS5731. We compared our own system board with TAS5731M attached and the TAS5731 EVM, we found the TAS5731 EVM is with flat THD+N vs frequency plot than our system board:

1W, 4ohm load:

Left: TAS5731 EVM, Right: System Board with TAS5731M -> Any potential problem to get low THD+N at 300Hz, high THD+N at 5kHz? How to improve it?


10W, 4ohm load: Left: TAS5731 EVM. System Board with TAS5731M -> Any potential problem to get very high THD+N at 300Hz at low band? How to improve it?




Thank you and Best regards,

Wayne Chen
09/29/2016

  • 0
    TI__Guru 57800 points

    Hi, Wayne,

    Thanks for your question. were the amplifiers configured with the same settings?, I'm asking because the power response seems quite different. The second plot of the system board makes me think that maybe a saturation event is happening as the THD+N gets really high (20%). Can you please share the register setting used to configure the amplifier in the system board?

    Thanks and Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    TI__Genius 15950 points

    Hello Diego,

    Thank you for your concern. The schematic, LC filter values, I2S sample rate and software configurations are exact the same (no DRC, no EQ, same 0x05, 0x07 setting). The only difference is power supply. The system board uses onboard boost converter (12V -> 18V) and the EVM uses external 18V power supply unit. Does power supply quality (ripple, current rating) impact the THD+N vs frequency plot? If yes, which power supply parameters should be check (make FFT plot of the power supply voltage?

    Thank you and Best regards,

    Wayne Chen
    09/30/2016

  • 0 in reply to Wayne Chen (Audio AE)
    TI__Guru 57800 points

    Hi, Wayne,

    Thanks for your response. If the power supply in customer's board is not capable of delivering enough current, the amplifier's outputs can show a saturation event. I would recommend you to power up the customer board with the power supply used to power up the EVM just to discard any issue on customer's power supply. In general, the effect of the ripple in the power supply can be reduced if the amplifier has good bulk capacitors close to the PVDD pins.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    TI__Genius 15950 points

    Hello Diego,

    Addition, would you pls advise the possible reason to make THD+N spike I marked in red?



    Thank you and Bst regards,

    Wayne Chen
    10/07/2016