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Audio amplifier with Line out usign DAC + D Class amp

Miroslav Bozic
Intellectual 420 points
Part Number: PCM5121TPA3138D2
Other Parts Discussed in Thread: TPA3138D2, PCM5122

Dear team,

I am working on the design that should include an audio interface with the following requirements:

  • It should receive digital audio data from the MCU
  • It should have Line out
  • It should be able to drive four 1W/8Ohms speakers (every two speakers are connected in parallel per amplifier channel)

I have designed the schematic diagram using mentioned ICs from TI and will appreciate if you can review the connection between PCM5121 and TPA3138D2 as well as the Lineout circuit. The power amplifier will be powered with the fixed 5V, so at the 4Ohms load (two 8Ohms speakers connected in parallel), there shouldn't be more than ~2.5W which is suitable for the used speakers. I will limit volume in order to limit the output power in the firmware.

Please find attached schematic.

Thanks in advance.

  • 0
    TI__Guru 53573 points

    Hi Miroslav,

    In general, I recommend that SCK source be the base clock for your audio source, as they need to be synchronized.  What is generating the I2S signals? Can the share the same clock as the SCK? Otherwise it would be better to just use the device in 3 wire mode to avoid synchronization issues.  

    Not that the PCM5122 has a 2.1Vrms output.  The TPA you have selected as a gain of 20dB minimum.  So that would mean that your fullscale output is 21VRMS, which is much larger than your supplies.  I just recommend you use the attenuation registers inside the PCM5122 to reduce the full-scale maximum output.

    Otherwise this looks good,

    Please respond with any additional questions,

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Intellectual 420 points

    Hi Paul,

    thanks for the feedback you have provided.

    The PCM is I2S master so it will receive a clock from the oscillator and provide Frame and Bit clock to the microcontroller. So the MCU and DAC will be communicating in 3 wire mode.

    You are right about the PCM output and TPA gain, definitely we will limit the output power of the PCM to avoid clipping.

    Best regards.