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TAS5713 "click" on audio startup

DJ
Prodigy 225 points
Other Parts Discussed in Thread: TAS5713

We are using the TAS5713 digital audio amplifier in a product. The chip is configured in PBTL mode for a single channel audio output. We have working product/firmware and just completed a pre-production build of 110 boards. During production test of the boards, we discovered > 10% of the boards have a very annoying "click" at the startup of audio playback. This click is independent of the volume control setting. We have played with the settings for the STOP/START PERIOD REGISTER and all this does is delay the time to when the click is heard when starting up the audio. I suspect this relates to taking the part out of shutdown mode. All boards were tested with the same speaker attached to rule out this being an off-board hardware problem. Anyone seen similar problems with this part?

 

Thanks,

Dave

  • 0
    TI__Guru**** 189399 points

    Hi, Dave,

    Hey, I apologize, we completely missed your post. Did you get this resolved?

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 225 points

    Don,

    I figured you might be on vacation without your laptop or iPhone ;-).

    This has not been resolved, albeit we chose to implement a temporary band-aid on the problem not putting the PA chip in shutdown when audio is not playing. This means that our power consumption is about doubled when the product is sitting idle, although it turns itself off after a relatively short period of time (5 min.) under these circumstances.

    It is only when the unit is brought out of shutdown that this problem shows up. On most boards it isn't a problem, but on about 1/3rd of our boards it is noticeable, and on some boards it is downright obnoxious and unacceptable. I tried playing with the external SSTIMER capacitor value to slow down the output ramp time, but all this did was add a delay before you'd hear the click, i.e. no change in the sound or level of the click.

    One of the more interesting cases I found (we built 110 boards) was a board that only clicked some of the time, not all of the time. It didn't seem to follow any predictable pattern, but at the startup of the audio, it could either have no click at all or at other times have a very loud click. Very strange!

     

    Dave C

  • 0 in reply to DJ
    TI__Guru**** 189399 points

    Hi, Dave,

    Are you running in AD or BD modulation?

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 225 points

    Don,

    We are using AD modulation.

     

    Dave

  • 0 in reply to DJ
    TI__Mastermind 33420 points

    Hello Dave:

    Will you please try using BD modulation?

    -Tuan

  • 0 in reply to Tuan
    Prodigy 225 points

    Tuan,

    We tried BD modulation and the problem is gone! Now, I have a couple of questions:

     

    1. Why does this fix the problem?

    2. We have the recommended capacitor on the SSTIMER pin for AD modulation. If this part is left on the boards, are we going to have problems with running BD modulation (i.e. the datasheet indicates this pin should be left floating for BD modulation)

     

    Thanks,

    Dave C

  • 0 in reply to Tuan
    Prodigy 225 points

    Tuan,

    We tried BD modulation and the "click" on audio startup problem is gone!  We have the recommended capacitor on the SSTIMER pin for AD modulation. If this part is left on the boards, are we going to have problems with running BD modulation (i.e. the datasheet indicates this pin should be left floating for BD modulation)

     

    thx,

    Dave