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TAS2781: Max. 50 ms Beep from Beep Generator

Stefan Zoller
Prodigy 20 points
Part Number: TAS2781

Hi,

I'm using the TAS2781EVM to test the Beep Generator feature of the TAS2781 using the SDZ pin. No software is running on the PC, just power and the SDZ signal is applied.

Applying 55 kHZ and 50% duty cycle to the SDZ pin starts the beep generation as expected, but it stops after 50 ms despite the PWM is still active. Generating several beeps in a row with a burst signal is possible and shorter beeps can also be created. But I can not get past the max. length of ca. 50 ms what is not expected according to the datasheet.

CH1: SDZ pin
CH2: OUTP pin

Please advise.

  • +1
    TI__Mastermind 18985 points

    Hi Stefan,

    this is a limitation on the device. when toggling the SDz pin the beep can only be 50ms. We need to add this to the datasheet. 

    You can also generate the beep of any duration from the NC_SCLK pin . in this case pin 17 will need to be connected to 1.8V. and the Mode pin will need to be connected to AVDD. 

    However in this mode I don't think the I2S bus will be functional. 

    Regards,
    Arthur

  • 0 in reply to Arthur Brown
    Prodigy 20 points

    Hi Arthur,

    thanks for the fast reply. Ok, than it's not a bug, but classified as feature :)

    I just tested the beep generator using the NC_SCLK pin, now it can create long beeps.

    Regards

    Stefan

  • 0 in reply to Stefan Zoller
    TI__Mastermind 18985 points

    Hi Stefan, 

    Did you also have to connect the MODE pin to AVDD?

    Regards,
    Arthur

  • 0 in reply to Arthur Brown
    Prodigy 20 points

    Hi Arthur,

    yes I did connect the Mode pin to AVDD when using NC_SCK. With Mode = GND it does not work.

    Also I made some more measurements using the SDZ pin. When I fully configure the TAS2781 and then interrupt the playback I can create long beeps. So the limitation of 50 ms is not universal, but only applies if the IC is not configured. This is odd, as I first pull SDZ low for some milliseconds to enter the software shut down mode.

    Or there is some limitation on the EVM. Can you give more technical insight about the limitation of the beep generator?

    Regards,

    Stefan

  • +1 in reply to Stefan Zoller
    TI__Mastermind 18985 points

    Hi Stefan, 

    thank you for the information, We will do some investigation to understand which register setting is letting the beep work for longer than 50ms. (this is news to us)

    but other than that there are no other limitations to be aware of. 

    Regards,
    Arthur

  • 0 in reply to Arthur Brown
    Prodigy 20 points

    Hi Arthur,

    ok take your time and let me know the results.

    One more note, when interrupting the playback with the beep, not only the registers are set up but also the clock on the I2S interface is applied. The difference may also be there.

    Regards

    Stefan