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Trying to convert USB audio to analog

Rob Helvestine1
Intellectual 295 points
Other Parts Discussed in Thread: PCM2706C, PCM2704C, PCM2912, PCM2903, PCM2901

Hello,

I have an application where I have USB audio and am trying to convert it to analog for use in a standard 3.5mm audio jack. I'm unsure of the parts that go in between the USB hub and the audio jack. Does TI sell an IC that can convert the signals from USB audio to analog, and do any needed amplifying? 

Thanks,

Rob

  • 0
    TI__Guru 53913 points

    Yes, please take a look at the PCM2704C or the PCM2706C.  These devices act as a USB audio bridge and feature a headphone amplifier as well.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Intellectual 295 points

    Thanks Paul. These devices seem to be what I'm looking for. I also need a microphone input, which I don't see on the datasheets. Is there another USB audio codec that has a microphone input? 

    I also need to support push-to-talk (PTT), but I believe that is handled external to the codec. 

    Additionally I need to support USBPD. This can be done by routing the D-/D+ pairs also to a microcontroller with a PD controller, possibly with a mux in between. Are there any microcontrollers / PD controllers that have built in USB audio codecs?

    Thanks,

    Rob

  • 0 in reply to Rob Helvestine1
    TI__Guru 53913 points

    You can also look at the USB codec devices, like the PCM2912.

    In regard to the microcontroller questions, you might what you check in on the Embedded Processing forums at e2e.ti.com, but to my knowledge, we do not have an MCU+CODEC.  We do have some DSPs that might be able to interact with an external DAC and ADC, but that would probably be a significant development.  You could also check out XMOS or Cmedia's solutions.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Intellectual 295 points

    Paul,

    Thanks for your help. I need a self-powered (3.3V) solution and noticed the PCM2901/PCM2903 options. They have VinL/R pins for differential analog microphone input (I assume). As my microphone input is from a typical audio jack connector (TRRS), I'm assuming I can just ground one of those VinL/R pins and connect the other to the microphone analog input? Just a different microphone input compared to the PCM2912 so wanted to double check. 

    Thanks,

    Rob

  • 0 in reply to Rob Helvestine1
    TI__Guru 53913 points

    Hi Rob,

    That should be fine, but you should verify that your microphone output does not exceed the analog input limits as specified in the datasheet.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Intellectual 295 points

    Paul,

    The PCM290x and PCM2912 are too large. I'm considering using our microcontroller on the board to convert the USB audio into an I2S bus. I'm taking a look at TI's options for I2S audio codecs and they all seem a little overkill for my application. I'm just trying to interface to a standard 3.5mm TRRS audio jack, so two analog outputs for L/R, and one analog input from a microphone. Does TI have a basic audio codec to interface with the 3.5mm audio jack? 

    Another option is to output the analog audio directly from the microcontroller into a headphone preamplifier. This application has to be as small as possible as it is embedded inside a cable. 

    Thanks for any input,

    Rob

  • 0 in reply to Rob Helvestine1
    TI__Guru 53913 points

    Hi Rob,

    As far as I know, we do not have the very small codecs required for the in-line USB C to headphone cables.  We do have some small digital input headphone amplifiers.  I recommend looking at some of the TASxxxx headphone amps.  You could also look at this device:

    Thanks,

    Paul