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PCM2906C: Suspend Signal and Input operation

Part Number: PCM2906C

Hello,

I am designing a circuit using the PCM2906C and in the eval circuit I see that the suspend signal from the codec is connected to the enable circuit of the regulator and this same circuit powers the input amplifiers.  If the IC goes into suspend after 5ms of inactivity on the USB line, and USB activity is what wakes it up, how do the input lines have power in their OP2353UA and how does the IC know when audio is coming in to be processed?

Thanks,

Adam

  • Hi Adam,

    The device does not record or playback audio without USB communication initiating this process so it is never necessary to have the input or output amplifiers powered up if you are not actively trying to record or playback audio. The USB bus wakes up the device, not the analog input. If you were looking for a wakeup from audio you would need to monitor this and issue a flag to your USB enabled device to tell it to start recording. 

    Best,

    Zak

  • Hi Zak,

    Ok that makes sense, and brings up a secondary question. Our final application will use a presence sensor to indicate when the codec should activate and being its functioning.  What would you recommend as the best test software to use for this codec without being implemented in the system? My first design with this is a test circuit to evaluate the audio quality coming through our schematic and I need to pass in and out canned signals. I looked through the user manual of the eval kit and it doesn't provide much guidance into how I can evaluate the initial receiving of the board to check audio quality, before we have the software in place to monitor and initiate recording/playback.

  • Hey Adam,

    I'm sure it's not the best software, but Audacity is a good free option for capturing USB audio that I regularly use. It has its quirks but is pretty easy to use and even includes some measurement and analysis tools for the recorded data so it might be a good place to start!

    Best,

    Zak