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PCM2912A: 6MHZ XO OSC

Part Number: PCM2912A

Hello, 

I want to use an external 6MHz crystal OSC instead of a crystal resonator for the PCM2912A due to space constraints. The datasheet mentions they dont recommend this since you cant use sspnd to disable the clock. Accordingly to section 9.3.11.4 in the DS, the PCM2912A enters a suspend state when it sees a constant idle state on the USB bus after approximately 5 ms. Will there be any issue if we still have a 6MHz input clock during this suspend state? 

Thanks,

Amy

  • Hi, Amy,

    There should be no issue with leaving the clock during suspend state. The PCM2912A requires an operational 6MHz clock that should be valid while the codec is operational; it is unhealthy for the device to loss the clock source while powered on. This is not a problem with the use of a crystal resonator because the PCM2912A is receiving the clock source at all times. A crystal oscillator can be used as long as the clock signal is valid during all the time the codec is operating and the digital levels are compliant with the recommended operating conditions of the datasheet.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • Thanks Diego. The only problem I can think of is that the power for the codec would come up before the power for the osc. Would this cause an issue?
  • Hi, Amy,

    If the device is powered before the oscillator, the codec may malfunction, the clock is required for the device since power-up. Unfortunately, we cannot guarantee the correct performance of the device under the mentioned condition.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • Hey Diego, is there a way to delay the power up of the codec until the ref clock is up?
  • Hi, Amy,

    Unfortunately, it is not possible as the device does not have a signal to hold the device until the clock is  provided. Perhaps an option would be to keep the Vbus below 2.5V until the clock is provided as it will hold the internal reset sequence.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • OK, Thanks. I will just go with a 6MHz crystal resonator.

    Amy