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TAS5727: High-pitched whistle on "exit shutdown" command

Marshall Mucasey
Prodigy 30 points
Part Number: TAS5727

Whenever the "exit shutdown" command is sent (value of 0x40 to register 0x05) in preparation for normal operation, the TAS5727 plays a high-pitched whistle that lasts exactly the time specified by register 0x1A. Once the whistle stops, normal operation begins without any issues. It is worth noting that in this particular application, there are two TAS5727 chips each with a low- and high-frequency output (woofer and tweeter). The whistling (~2.5-3 kHz) is more prominent in one chip. Both TAS5727 units are held in shutdown mode after power-up initialization until audio playback is needed.

Let me know if there is any more information that might be useful in diagnosing this problem.

Thanks,

Marshall

  • 0
    TI__Guru 57800 points

    Hi, Marshall,

    Welcome to E2E, Thanks for your interest in our products!.

    After exit shutdown, the device turns ON the power stage softly to avoid noise artifact issues. If the amplifier is not muted before exiting shutdown, then, the amplifier will try to stream audio through the outputs during ramp-up process. This might cause noise problems during power-up, could you please check if the amplifier is not unmuted before exiting shutdown?. Could you please share the register configuration sequence for enter/exit shutdown mode of the amplifier?.

    Thanks and Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 30 points

    Hi Diego,

    Thank you for your response. To mute the amplifier I have been simply muting the master volume (setting register 0x07 to 0x03FF). Doing this just before exit shutdown (setting register 0x05 to 0x00) still causes the whistle. Is there more that needs to be changed before exit shutdown? Should I be using the soft-mute register instead?

    Thanks,

    Marshall

  • 0 in reply to Marshall Mucasey
    TI__Guru 57800 points

    Hi, Marshall,

    Thanks for your response. Muting the amplifier with register 0x07 should be enough, so the problem might not be related to the exit-shutdown register sequence.

    The TAS5727 also features an SSTIMER feature that is required when AD modulation is used to avoid noise artifacts during powerup. This is accomplished by connecting a capacitor between SSTIMER pin an GND. Altough this cap is not required when BD modulation is used, in some systems, using the cap helps reducing problems during startup. Bit D7 of register 0x1A should be set to enable SSTIMER feature. Do you have SSTIMER cap populated in your design?. Also, can you please share the schematic of the TAS5727 in your design?.

    It would be useful if you can take some captures of the output of the amplifier to check if the noise signal can provide any clue of the root cause.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 30 points
    Hi Diego,

    Unfortunately, I don't have access to the schematic right now, but I could try to get it for you. I do know that there is a 2200pF capacitor on the SSTIMER pin, that the TAS5727 should be set to AD mode (according to register 0x20), and that the SSTIMER function should be enabled (clearing D7 in register 0x1A according to the datasheet).
  • 0 in reply to Marshall Mucasey
    TI__Guru 57800 points

    Hi, Marshall,

    Yes, if SSTIMER cap is populated, the powerup process should work as expected. Could you please also take some captures of the output of the amplifier, before and after the amplifier?

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer