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LMX2592: Sync LMX2592 with other PLLs?

ikon
Genius 5355 points
Other Parts Discussed in Thread: LMX2592

Hi Support,

1. Does TI has a solution to synchronise multiple PLLs?
Customer will be using multiple PLLs using the same reference clock to generate different frequency tones.
They are concerned with the phase match of the these 2 tones.

2. Customer is evaluating the use of the LMX2592 for their new design.
However, the sync pin is not available on the LMX2592.
Is there another technique that is used to sync this PLL with other PLLs?

Thanks.

  • 0
    Genius 5355 points

    Hi Support,

    In addition, customer is using a 100MHz clock.

    All the clocks are the same.

    Customer's intentions are to use the PLL generate different fixed frequencies, so the output frequencies will be fixed during the operation.

    Lastly, would there be a difference if use a different reference frequency?

    Provided the same 20logN rule applies for the phase noise of the clock.

    Thanks.

  • 0 in reply to ikon
    TI__Expert 4085 points
    Hi Ikon,

    Thanks for your question. The LMX2592 applications expert is working on this and will get back to you.

    Regards,
    Julian
  • 0 in reply to Julian Di Matteo
    Genius 5355 points

    Hi Julian,

    Any feedback?

    Thanks.

  • 0 in reply to ikon
    TI__Mastermind 28001 points
    ikon,

    I think that maybe this application might not need a sync pin.
    The LMX2592 does not have a sync pin and an ambiguios phase can be created whenever there is division involved that is not in the feedback loop. However, I do not think that this is the case as this application can be done with the PLL_R = 1 and the VCO channel divider is bypassed, which looks like the case.

    The device can be used in integer mode so that the fractional engine does not need to be synchronized.

    If you choose a different reference frequency that does not evenly divide into the outptu frequencies, this would cause synchronization challenges.

    You can change the phase delay with MASH_SEED, but this requires the user to track the delay in a feedback loop and manually adjust. Sounds easier to me to just keep all in integer mode.

    Regards,
    Dean