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TAS5558 + TAS5624A SE Mode On/Off noise

Daniel Konrad
Prodigy 95 points
Other Parts Discussed in Thread: TAS5558, TAS5624, TAS5624A

Dear all,

I'm using a TAS5558 in combination with two TAS5624 amplifier ICs (6 channels, single ended configuration as described in the TAS5624A datasheet, p. 21). So far everything is fine, there's no pop or click noise when switching on the amplifier. But when I switch it off, there's a strange noise. It sounds like a discharging cap (swoosh noise). There's no better way to describe it.


My power off sequence is:


1. Mute  TAS5558 (Softmute all channels)

2. Pull down the reset signal of both TAS5624A amps -> this is when the swoosh noise occurs

3. Switch off TAS5558 (Channel shutdown in register 0x03 -> reset)

4. power off the unit

I've played around a little bit with several register settings in the TAS5558 and I get the best results when I skip the first step (soft muting the TAS5558). The swoosh noise is almost gone but then there's a quiet pop noise. So not an ideal solution.

Now to my questions:


1. Is there any recommended configuration for this setup (TAS5558+TAS5624 SE mode), e.g. register settings, power on/off sequence, etc.?

2. I've also tried the different PWM config setting (legacy lowZ, special lowZ, MidZ) but there's no difference at all. Can you recommend a setting?

Thanks for your help in advance,

Daniel

  • 0
    TI__Mastermind 33420 points

    Hi Daniel,

    First of all, let me answer your questions:

    1.  The sequence and register set-up you have are probably good.

    2.  For TAS5558, you can use mid-Z setting for now ... see my proposal below:

    Since Mute and Reset are digital signals, the assertion time is very short.  I assume that you have "split-cap" configuration for SE application and that you follow the data sheet guide for using 1uF on CSTART capacitor.  The ramp down period is ~ 1.1 sec.  Can you wait ~1.5 sec after Mute assertion and then assert Reset?

    Thanks,

    Tuan

  • 0 in reply to Tuan
    Prodigy 95 points

    Dear Tuan,


    thanks for your reply.

    I'm using a capacitor in series (TAS5624A datasheet page 21), not a split-cap configuration. Is MidZ still the preferred setting then?

    Increasing the delay between mute and reset did not help: the hiss noise is still there.

    Regards,
    Daniel

  • 0 in reply to Daniel Konrad
    Prodigy 95 points
    Dear Tuan,

    I found a solution: In my application automute was disabled and this caused the hiss noise during power on/off. Once automute is enabled powering on/off is perfectly quite.

    Regards,
    Daniel
  • 0 in reply to Daniel Konrad
    TI__Mastermind 33420 points

    Hi Daniel,

    Great.  I guess you only set it to automute when turn on/off.  While running, you'll turn automute off for pop/click prevention?

    Have a good weekend.

    Thanks,

    Tuan

  • 0 in reply to Tuan
    Prodigy 95 points

    Hi Tuan,

    yes, during normal operation automute is switched off.


    Regards,
    Daniel