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LM3886 mute circuit?

Artie Hall
Prodigy 20 points
Other Parts Discussed in Thread: LM3886

In reference to the LM3886 datasheet, fig. 1: Rm/Cm control the mute circuit. My understanding is that Cm is used for on/off timing. If I need the mute function to occur almost instantly, can I just omit Cm? Or should I make it some very small value? nf's or pf's?

Thanks all;

Artie

  • 0
    TI__Guru 52115 points
    Hi Artie,

    I will take a look at your question and get back to you soon.

    Andy
  • 0
    TI__Guru 52115 points

    Hi Artie,

    Here are some useful comments from my colleague:

    "Yes,  customer can remove Cm if customer doesn’t care pop sound in Mute On/Off. If customer worried about pop sound in Mute On/Off, I will recommend to use Cm.

    This mute operation is switched from signal pass Gm to Mute Gm when customer makes Mute mode from

    enable mode. At that time due to Vos different between signal pass Gm and Mute Gm, sometime makes pop.

    To avoid audible pop sound, Rm, Cm makes kind of fade-in and fade-out behavior. This make smoothly switching Gm."

    Andy

  • 0 in reply to Andy Liu (BMS)
    Prodigy 250 points

    I would recommend to have some delay. This mute function and under voltage protection creates a very pleasant switch on and switch off performance. Check out these oscilloscope pictures. Really nice behaviour! (I have designed the pcb if you wonder... :)  but I have no spares at the moment.)