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TPA3126D2: POP/Tick Noise on Power Down Sequence

Jay Yoo
Intellectual 2641 points

Part Number: TPA3126D2

Hi team,

I'm seeing a pop/tick noise during power-down with TPA3126 in a soundbar application and would like your guidance to remove the noise.

Conditions

  • Load: 6 ohm
  • PVDD: 24 V
  • Input/configuration: Differential / BTL
  • Modulation: Hybrid mode

Power-down sequence

    • MUTE --> SDZ pulled low --> DAC off
    • *PVDD is keep alive.

H7_1.png

Even with this sequence, a short tick noise is still audible, mainly during SDZ is pulled low I assume.

Could you please give any advice to reduce this noise?

Thanks,

Jay

  • 0 in reply to Jay Yoo
    TI__Mastermind 22220 points

    Hi Jay,

    Pop/click is typically due to impedance mismatch at the inputs, make sure the input components used have a tight tolerance. 

    Can you try reducing the input caps to 0.47uF?

    Regards,

    Sebastian

  • 0 in reply to Sebastian Muriel
    TI__Intellectual 2641 points

    Hi Sebastian,

    Thanks for your reply.

    I noticed that ringing on the output (post-LC filter) was affecting the tick noise at power-down. I assume the ringing created additional voltage on the output, causing an offset voltage and resulting in a differential voltage gap. The ringing appears to be caused by the LC filter's resonance, which is at 60kHz.

    After changing the switching frequency, adding a snubber for 60kHz damping, and modifying the inductor, the ringing and noise have been eliminated.

    I also tested with the EVM, and when I changed the switching frequency to 600kHz, I observed the same ringing only on the right channel.

    Could you please confirm why this ringing occurs with this device and check if the ringing is caused by LC filter resonance?

    Thanks,

    Jay

  • 0 in reply to Jay Yoo
    TI__Mastermind 22220 points

    Hi Jay,

    As you noticed there is a high frequency signal located near the LC filter cut-off frequency (resonant frequency). If the q factor value of the LC network is high, these high frequency harmonics can be amplified.

    Also the Q value of the LC filter network is related to the speaker impedance. If the speaker impedance increases significantly near the resonant frequency of the LC filter, the Q value of the filter will be very large. 

    Regards,

    Sebastian