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Original question:

ADC12DJ3200EVM: Software Driver support

ADC12DJ3200EVM: External Clocking

Anthony Rogers
Intellectual 340 points
Part Number: ADC12DJ3200EVM
Other Parts Discussed in Thread: LMK04828, LMX2582

We have an application where we would like to use the on-board clocking devices (LMK04828 and LMX2582) with an external oscillator. I see a 10 MHz input (CLKIN0) that seems to be only mentioned in the EVM manual briefly, but I want to ask to see if I can use this instead of connecting the signal generators and modifying the EVM. Is there a way that I can just use an external 10 MHz oscillator with the existing clock circuitry?

Thanks,

Anthony

  • 0
    TI__Mastermind 20090 points

    Hi Anthony,

    I only see the mention of the 10MHz reference lock in-between signal generators.

    Can you let me know what page of the user guide you are referring to please?

    Is your intent to use an external 10Mhz oscillator to clock the LMK04828?

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    Intellectual 340 points

    Hi Rob,

    On page 20 (Figure B-1), I see a 10 MHz reference mentioned, but I think this is for locking the signal generator to the signal input.

    My intent is to use an external 10 MHz oscillator to clock the LMK04828 (in lieu of the onboard reference).

    Thanks,

    Anthony

  • 0 in reply to Anthony Rogers
    TI__Mastermind 20090 points

    Hi Anthony,

    I understand. It would be best to use on the on-board 100MHz Crystek oscillator that is on the EVM already. Otherwise, you can use a 10MHz oscillator, if you have something with that same footprint. You cannot use the CLKIN0 in for this unfortunately.

    However, if you do change to a 10MHz oscillator on the EVM, then the performance will suffer even more and the LMK will possibly need some additional spi writes to get this to work.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    Intellectual 340 points

    Thanks Rob for the explanation! Main reason I wanted to switch the oscillator was to go to an external one with better stability/phase noise, like a TCXO/OCXO. I see I can use a signal generator to create an improved sampling clock, but was hoping that there was a way to feed in a 10 MHz (or 100 MHz) clock that would go into the LMK04828, as that would be a bit more reflective of our use case. I saw CLKIN0 listed as 10 MHz, so thought that may be a way to feed in a 10 MHz external clock, but I understand now that is not possible.

  • 0 in reply to Anthony Rogers
    TI__Mastermind 20090 points

    Hi Anthony,

    You can always modify the EVM to pipe in an external OCXO where the 100MHz reference oscillator is now.

    That is what I would do. or use an external sig gen as you noted.

    Regards,

    Rob