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TPA2015D1 Gain Control Question

William Leven
Intellectual 2440 points

We have a situation where the speaker connected to the TPA2015D1plays very softly.  On the schematic, the gain control is set to 15.5dB by floating the gain pin to a test point.   I suspect that we may be only getting the 6dB gain because the TPA2015 is seeing GAIN as grounded.  I have not seen a control done this way before, and it looks a little dangerous to me. 

Do you have any experience on how the schematic for setting this pin should be done, and how reliable leaving the GAIN pin floating to a test point would be?

  • 0
    TI__Genius 16645 points

    Hi Will:

    The GAIN pin is biased and read at power up.  When it floats, it is ~Vdd/2.

    When they run a trace off of it and if their board has leakage (dirty) it could possibly be read as a low for 6dB of gain.

    Also, probably not part of the gain concern, they should raise the voltage rating on their boost cap to 16V to allow for derating of the cap due to DC voltage bias, temperature, and tolerance.  A 10V cap is probably OK, but a 16V cap would be much better.

    Also, what is the supply voltage to the amplifier when the gain test is ran?  Remember the amplifier gains down if the supply voltage is low.

    Rgds,

    Fred

  • 0 in reply to Fred Shipley
    TI__Intellectual 2440 points

    Thanks Fred.  The test is being conducted while the device is powered over the USB port and hopefully with the battery close to full charge, although I will double check.

    -Will