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TLV320DAC3100: Output signal waveform produces distortion as power increases

Yuxi Liu(Tony)
Intellectual 1790 points
Part Number: TLV320DAC3100

Tool/software:

Hi TIer

My customer use TLV320DAC3100 in patient multi-parameter monitor .

Issue: My customer use TLV320DAC3100 to drives a 2W 4ohm speaker with signal distortion as output power increases over time, a distortion waveform at approximately 1.72W output, and a significant chirp of the in alarm sound.

Circuit like:

Waveform like:

As the volume increases, the drive waveform changes from a sine wave to a triangle.

Could you give me some suggestion? Thank you very much.

  • 0
    TI__Intellectual 1950 points

    Hi,

    This looks to me like this is the DRC (dynamic range compression) of the device kicking in. This is to help avoid clipping in the output. You may want to adjust the DRC threshold value to avoid DRC kicking in this early if this is the volume of the intended use of your device. DRC threshold is described in section 6.3.10.4.1 of the datasheet. 

    Let me know if you need any more help.

    Best,
    Mir

  • 0 in reply to Mir Jeffres
    TI__Intellectual 1790 points

    Hi Mir

    We try to change DRC to be low or large .

    But it also have signal distortion.

    Do you have more suggestion?

  • 0 in reply to Yuxi Liu(Tony)
    TI__Intellectual 1950 points

    Hi Tony,

    What pins are you checking the output on? Also, what voltage are you supplying to the device? I calculate from your distortion that you said at 1.72W, you are distorting at 2.6V. If your SPKVDD is 3.3V, I can imagine you would be distorting, looking at section 4.12.2 in the device datasheet. You will want your SPKVDD to be maxed out at 5.5V (referenced to SPKVSS) to not distort at power levels around 1.72W.

    Best,
    Mir

  • 0 in reply to Mir Jeffres
    TI__Intellectual 1790 points

    Hi Mir

    We looked at the customer's schematic and found that waveform distortion occurs after AC coupled capacitance, before the yellow curve and after the pink curve. The reason customers are using polarity capacitors here is because they want to make "horn off alarm" notes based on our application. So can you give a little advice, is the selection of capacitance inappropriate?

  • +1 in reply to Yuxi Liu(Tony)
    TI__Intellectual 1950 points

    Hi,

    Sorry about the wait.

    Can you remove the 10uF capacitor and short out the inductor after your speaker output? You should not need an LC filter for the speaker output, and it looks like maybe the filter is overloading the output. Let me know if this doesn't fix the issue.

    Best,
    Mir