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ADS5562EVM: ADS5562EVM - CDCE72010 Modification - Direct feed in of low jitter clock

rwong1231
Prodigy 80 points
Part Number: ADS5562EVM
Other Parts Discussed in Thread: CDCE72010

Hi,

With respect to the user guide slwu061a (page 13), I was wondering if this 4th option might work:

In the VCXO pad, instead of using a VCXO, I would solder on a low jitter (<0.4ps) VCO (not VCXO) clock of 200MHz with the same footprint and pin-to-pin match to the TCO-2111T. I would also cut the feedback trace from the Loop Filter to the VCXO and keeping the original factory setting of the CDCE72010 for the Output Divider (P) of 4 --> ie 200MHz in...and 50MHz out. I'm not concerned with syncing the ref clock.

Thus, I won't have to configure the EEPROM and still use a differential LVPECL clock. This would work only if the CDCE72010 passes through the clock independent of the feedback.

Will this work? Or does the CDCE72010 lock up if I don't use a reference clock and I don't use the feedback mechanism?

Thank you.

  • 0
    TI__Mastermind 29220 points

    Hi,

    I see no issue with installing a fixed frequency oscillator in place of the VCXO, especially after looking at the block diagram of figure 1 of the datasheet.  But for specific behavior of the device I think you would need to consult the clocking forum directly.  but as far as I know there should not be an issue with a fixed frequency oscillator.

    Regards,

    Richard P.