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LMX2592: Long Term Phase Synchronization

Ed Shultz
Prodigy 30 points

Part Number: LMX2592

I have an application in which I need to ensure phase synchronization to within about 10 degrees between multiple synthesizers over a long period of time (months) with or without power cycling.  I would like to know if the LMX2592 is a suitable device for this.  If I synchronize and set the relative phase relationship of multiple LMX2592 synthesizers connected to the same frequency reference per the information in the datasheet, will the relative phase relationship between the LMX2592 synthesizers stay fixed over a long period of time?  Will the relative phase relationship stay the same, if I power cycle occurs and the synthesizers are re-programmed back to their original settings?  I'm concerned that they may drift apart over time or noise on the reference signal might affect the long term synchronization.  

  • 0
    TI__Guru** 119750 points

    Hi Ed,

    We don't have solid answer but I would guess yes, the phase will change as it is temperature dependent.

    if you have direct VCO output (i.e without using the divider) and the output frequency is an integer multiple of the reference clock, then the output will has a deterministic phase relationship w.r.t the reference clock, after each power cycle. Part to part variation is expected and it will change with temperature.

  • 0 in reply to Noel Fung
    Prodigy 30 points

    Hi Noel,

    Thanks for your quick reply.  I'm thinking that I can calibrate out any part to part variation and my temperature range is small so that doesn't worry me much.  However I would like to know if you think there would be any reason to expect a continuous drift in the relative phase over time between two LMX2592 synthesizer for some other reason.  For example, if I setup two LMX2592 evaluation boards that are connected to the same 100MHz reference, set the output frequency of both boards to 2500MHz and then set the relative phase between the two boards to something like 90 degrees by adjusting the phase of one of the boards.  I then let them run in this state for days or weeks.  Would you expect the relative phase to vary around 90 degrees or would there be any effect in which the relative phase would slowly drift away from 90 degrees and be at some completely different phase after days for weeks?

  • 0 in reply to Ed Shultz
    TI__Guru** 119750 points

    Hi Ed,

    I don't have data to support, but I would expect there will be some drift but overall speaking the phase difference is still close to 90 deg. 

  • +1 in reply to Noel Fung
    Prodigy 30 points

    Thank you for your opinion on this!