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Original question:

TPA0253: driving BTL mode from a balanced source

TPA0253: TPA0253DGQ

Eric Conner
Prodigy 150 points
Part Number: TPA0253

We are using TI par TPA0253DGQ to drive a handset. We are noticing that if the SHUTDOWN pin is held low, the audio level is reduced but not totally muted. I do not see anything in the data sheet that show how much attenuation to expect. Can you please advise.  Thanks!

  • 0
    TI__Guru** 101525 points

    Hi Eric,

    I'll check if we can have the attenuation spec from a similar device. Also it could be the signal flows from input to output through the feedback resistors of the internal components.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 150 points

    Ok, Because the term Shutdown implies that it should be better than a Mute. Very curious why this is happening.

  • 0 in reply to Eric Conner
    TI__Guru** 101525 points

    Hi Eric,

    I understand the concern, I haven't found this spec for similar devices. I'm checking now for any previous char data for this or similar projects.
    I'll let you know of any findings early next week or before if possible.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    TI__Guru** 101525 points

    Hi Eric,

    Whenever a device has only either shutdown or mute, the term is pretty much interchangeable and takes the device into a low consumption mode.

    I've been trying to look for spec data for similar Class-AB devices, the most I could find is ~70dB attenuation during mute or shutdown. If you compare the output signal before and after the shutdown, how much attenuation could you measure?

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 150 points

    I'm seeing only about a -15db attenuation. We are using this as a handset driver and when it is muted, the audio can still be heard. Definitely with reduced volume but we would like it to be OFF or -70dB would be acceptable. So, it does not seem to be either a mute or a shutdown.

    (Typically SHUTDOWN means low power mode and sometimes takes extra time to come alive. Whereas MUTE, usually just shuts off the output with minimal recover time.)

    Do you have an alternate part we could use or recommended add-on circuit?

  • 0 in reply to Eric Conner
    TI__Guru** 101525 points

    Hi Eric,

    Could you share your schematic so we can take a quick review?
    If you remove the power from the amplifier, do you see now a considerably higher attenuation?

    Best regards,
    -Ivan Salazar
    Applications Engineer