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TLV320DAC3100: Speaker output waveform

Ashwini M S
Prodigy 90 points
Part Number: TLV320DAC3100

Hi,

I am using TLV320DAC3100 Audio amplifier IC. According to the datasheet the speaker output signals SPKM & SPKP are Inverting and Non-Inverting signals .But I got below waveform when  SPKM and SPKP signals are probed.

Is this is the expected waveform or I  am getting wrong waveform?. Can you please provide the expected speaker output waveform.

Also I have one more query.
I am hearing hissing sound while audio is playing. whether I need to add any external filter to reduce this noise. Please suggest.

  • 0
    TI__Guru** 102545 points

    Hi Aswhini,

    The waveforms you show are correct for a silence playback at the Class-D output. As the input signal increases you should see the duty cycle adjusting. You can refer to BD modulation on this document: https://www.ti.com/lit/an/slaa701a/slaa701a.pdf?ts=1652735991366#page=6&zoom=100,0,97

    Regarding the hissing sound, I'd like to ask a few things:

    • Are you using the EVM or a custom board?
    • What are your input clocks (MCLK, BCLK, WCLK) and what is the device sampling rate configuration (PLL and MDAC, NDAC, DOSR)?
    • Is it present only when playing audio, ie. is the hissing present if you play a silence audio file?
    • Is the hissing present if you mute the DAC?
    • Is the hissing present if you mute or disable the Class-D driver?

    Best regards,
    -Ivan Salazar
    Applications Engineer