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TPA3106D1: pop noise when switch on/off audio amplifier TPA3106D1

Filosofi
Intellectual 925 points
Part Number: TPA3106D1

Hi,
I've realized a audio amplifier stage for a medical application using TPA3106D1.
The input signal bandwidth is 5Hz to 50Hz.
Everything works fine but an annoying click is heard through the output speaker when I switch on/off (or even mute/unmute) the product.
Can you give me an effective advice to get rid of this undesired effect ?
I have attached the relevant page of the electrical schematics.

Best Regards,
Gabriele Filosofi

click_noise_on_tpa3106d1.pdf

  • 0
    TI__Genius 9140 points

    Hello Filosofi,

    some suggestions for avoid pop noise are:

    1. INP and INN should be balanced design. during switching on/off, there would be bias voltage setup/release,  if INN and INP are not balanced, then with same charge current into C33 and C39, the voltage ramp up speed are diffenrent, that means there is differnetial voltage generated at VINP-VINN, pop noise happen.  Soltion is: (a) add a resisor serial with C39, the value should be similar as U3A output impedance. (b)from layout, the two trace of INN and INP should be differential routing, and connect GND of C39 to close to U3A GND.

    2. make sure the seuquence should be:  AMP play -> DAC ramp up.    DAC ramp down -> AMP shutdown/mute.

    Dylan

  • 0 in reply to Dylan Yao
    Intellectual 925 points

    Hi Dylan,
    Thank you for your mindful answer.
    Fortunately I've fixed the problem in firmware. The trick was to ramp up/down the signal smoothly when I turn on/off the amplifier.
    The series resistor will be introduced when the board will undergo a revision.

    Kind Regards,
    Gabriele