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TAS5731: Question about capacitor at PVDD

Austin Do
Intellectual 2425 points
Part Number: TAS5731

Tool/software:

Hello team,

My customer is referring TAS5731EVM in their design(https://www.ti.com/lit/ug/slou331a/slou331a.pdf )

Can you please answer the customer's questions?

  • Speaker: 2W (max 3W), 4ohm
  • PVDD = 12V, AVDD/DVDD = 3.3V

1. For this speaker, is still needed to use 220uF aluminum cap? Can we reduce the capacitance and change the material of cap?

2. For this speaker, can we reduce the inductance also? Can you provide the guide for filter?

Best Regards,

Austin

  • 0
    TI__Intellectual 2425 points

    Hello team,

    One more question I have

    What is the meaning of below picture in TAS5731EVM? 

    "All speaker outputs are biased at VCC/2 and must not be connected to ground"

    Can you clarify if negative input can be connected to directly GND?

    Best Regards,

    Austin

  • 0 in reply to Austin Do
    TI__Expert 5115 points

    Hi Austin,

    The 220uF caps are used as a voltage divider to PVDD/2 and to help prevent pop noise in single ended mode. You can use slightly smaller ones but the performance may decrease. The inductance cannot be lowered by much. The datasheet mentions that the minimum inductance for that filter is 10uH. Lowering this value from 15uH could cause this value to be violated given the high tolerances of inductors. 

    Austin Do said:
    "All speaker outputs are biased at VCC/2 and must not be connected to ground"

    This refers to the DC offset of the device outputs. This means if you were to connect this node to ground, you would be shorting PVDD/2 to ground which will cause issues. The speaker itself can have an input tied to ground, but the PVDD/2 pin mentioned before on the EVM would be better.

    Regards,

    Ramsey

  • 0 in reply to Ramsey Foote
    TI__Prodigy 120 points

    Hi Ramsey,

    I am TSR paired with Austin. Can you please confirm which one is correctly understood? Connecting speaker (-) output to GND is possible, but biasing to VCC/2 is recommended to prevent pop noise? Or connecting to GND is not possible at all? Thanks!

  • 0 in reply to Kara Park
    TI__Expert 5115 points

    Hi Kara,

    Connecting the speaker (-) to ground would only be possible if you add a DC blocking capacitor on the (+) input. This is an error in the users guide. I would recommend the VCC/2 bias method. 

    Regards,

    Ramsey