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LM4860: Glitch appears when shutdown is released

Masanori Tachibana
Genius 5350 points
Part Number: LM4860

Hello support team,

I have a question about LM4860.

Our customer's speaker amplifier is configured like shown in the data sheet of Figure 3.


And mute function is controlled from SHDN (pin 2) through HP-IN1 (pin 6) as shown below.

As soon as mute is released, a glitch appears on the output signal as shown below.

[Question]

Are there measures to eliminate or reduce such glitch?
Please give me advice.

Best regards,
M. Tachibana

  • 0
    TI__Guru** 100575 points
    Hi Tachibana-san,

    Unfortunately there is no evaluation board available of this device for debugging.
    What value are you using for bypass capacitor (Cb)? Perhaps trying different capacitor values would change this behavior. I would say that this glitch is coming from the internal bias, do you perceive a pop-like noise when you release mute?

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Genius 5350 points

    Hello Salazar-san,

    Thank you for your reply.
    The bypass capacitor (Cb) of the customer's board is 0.1 μF.

    Is bigger capacitor Cb better for glitch?
    Is there side effect such as it takes time to return from mute?

    Best regards,
    M. Tachibana

  • 0 in reply to Masanori Tachibana
    TI__Guru** 100575 points
    Tachibana-san,

    Bigger capacitor should increase start-up time, by increasing this time it could help on reducing the glitch.
    Another option could be to reduce the input capacitor. The glitch might be coming from the charge/discharge of this capacitor.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Genius 5350 points

    Hello Salazar-san,

    Thank you for your comment.
    I'll inform the customer what you advised me.

    Best regards,
    M. Tachibana