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PCM2707 Clock

Benjamin Shaya
Prodigy 30 points

I am working on a USB to I2S system using the PCM2707. I have made a board according to reference schematic in the datasheet, but when I soldered everything up, the PCM2707 does not communicate with my computer. Further examination revealed that the oscillator does not start oscillating (instead, it looks like it just has noise across it). I have tried multiple chips and multiple crystal oscillators, but the problem persists. Are there nuances with the PCM2707 that are not documented in the datasheet?

I've attached my schematic and output waveform on the oscillator outputs.

  • 0
    TI__Guru**** 189401 points

    Hi, Benjamin,

    There shouldn't be any tricks here... Keep debugging. Check power, connections, etc.

    Sorry I don't have a magic bullet...

    -d2

  • 0
    Prodigy 20 points

    Hi, I don't know if it's me or your schematics, but where does "VDD" is linked? I didn't make my design yet so I'll probably say something wrong, but I think even if it's bus powered, VDD must be connected to a power supply.... Other solution would be using an integrated oscillator which generates a clock signal just when it's powered, and you just had to connect its output to XTI and let XTO opened.

    I hope you'll find the problem and succeed in makind it work, and sorry for my bad English.

  • 0 in reply to loic jacquinot
    TI__Guru**** 189401 points

    Hi, Benjamin,

    I see you have a diode in series with the USB power, and on the left of that, a 5V supply. This doesn't look like what we have in the d/s. Do you have a separate 5V supply, or is that an output?

    Can you try shorting out the diode and see if it works? The diode might be pulling your supply less than the min of 4.35V spec'd for the VBUS pin if you're using the power from USB.

    -d2