PCM2903: PCM2903 not detected on USB bus

We've incorporated a PCM2903 chip into our board design and followed the reference design in the datasheet. It is connected to a USB hub chip which then goes to our microprocessor. We elected to provide an external clock source for the 12MHz clock input on the chip.

Everything around the chip seems to be functioning properly however we are unable to have our operating system detect the chip. We've verified that it's not the USB hub or OS since we can detect when a PCM2902-based USB device is connected.

Some questions I have:

• Does the 12MHz clock input has to be present as the chip is powered up to work (ie, be detectable over USB)?
• Will the PCM2903 fail to boot up if the clock signal is outside the acceptable tolerance?