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PCM1681: Connection between PCM1681 and DRV135

Aman Shah71
Prodigy 210 points
Part Number: PCM1681
Other Parts Discussed in Thread: DRV135

Hello,

We working on a project in which audio takes from USB and provides output on XLR connectors.

In this project PCM1681 takes 4 stereo input from DSP (Via I2S Communication).

Output of PCM1681 (8 x Vout) feed in to 8 x DRV135 to get output on XLR connector.

Questions:

Do we need to place Low Pass Filter in between output of PCM1681 and input of DRV135?

Do we need to place any filter between output of DRV135 and XLR connector?

How much input signal voltage require for DRV135 at VIN?

Please suggest.

Also let me know if you need any other information.

Thank you.

Best,

Aman Shah

  • 0
    TI__Guru 54323 points
    Hi Aman,

    A simple RC filter with a fC above the audible range should be sufficient on the output of the PCM1681 to filter any out of band noise. In addition, a DC blocking capacitor is recommended on the output of the DRV135 to remove any DC bias issues, see figure 29 of the DRV135 datasheet. Assuming you have a 5V supply for the PCM1681, its output should be 3.75Vpp, so your differential output should be 6dB greater. Assuming you have sufficient voltage supplies for the DRV135. I do not believe there is any minimum input voltage requirements for the DRV135.

    Please let me know if that answers your questions,
    Thanks!
    Paul
  • 0 in reply to Paul_Frost
    Prodigy 210 points
    Hi Paul,

    Thank you for your response.

    We have placed DC blocking capacitor at the output of PCM1681. So, as you suggested if we place RC filter at output of PCM1681 then can we remove DC blocking capacitor of 10uF at Vout of DAC?

    And how much supply voltage do you recommend for DRV135 as Vin is 3.3V or 3.75Vpp? Can we use +/-5V supply voltage as supply voltage range is +/-4.5V to +/-18V in datasheet?

    Thanks!

    Regards,
    Aman Shah
  • 0 in reply to Aman Shah71
    TI__Guru 54323 points
    Hi Aman,

    I misspoke, you will still need the DC blocking cap on the input of the DRV as well to prevent the 2.5V bias of the PCM affecting the output. The DRV has a gain of 6db differential, so the each output pin of the DRV will have a 3.75Vpp signal. The DRV135 datasheet specifies the output swing as V+ (-3V) and V- (+2V), with no load. The +/-5V supplies satisfy this condition.

    Let me know if you have more questions.
    Paul
  • 0 in reply to Paul_Frost
    Prodigy 210 points

    Hi Paul,

    Thank you for your answer and support. I need to review part of schematic which have PCM1681 and DRV135 for our application. So can you provide me your email so that I can share it and get reviewed it by you.

    Thank you.

    Best Regards,
    Aman Shah

  • 0 in reply to Aman Shah71
    TI__Guru 54323 points
    Hi Aman,

    I will send you an invite to connect on the e2e forum, then we can discuss this over email. Thanks!