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LMX2594: issue about phase synchronization of two lmx2594

user5959213
Intellectual 865 points
Part Number: LMX2594
Other Parts Discussed in Thread: TIDA-01410, LMK00304

Hi all,  

      We have an application require two outputs of lmx2594 working at the same frequency and phase for beam steering.I have read your reference design TIDA-01410.But there is something different in our design for some reason.The design diagram is as follow and our application belongs to SYNC category 3 :

  For the design,i have some questions:

1.Is there some output skew from the  lmk00304?

2.Should the trace length from the lmx00304 to two lmx2594 be equal?

3.Is it right for ocsin should be lower than 100M for SYNC category 3?

In short, can the above design realize the synchronous output of two lmx2594?

 

BR.

hips

  • 0
    TI__Guru* 88940 points

    Hi Hips,

    1. yes, skew exists between outputs of LMK00304, datasheet has the numbers.

    2. Yes, trace lengths should be controlled so that OSCin and SYNC signals arrive at the LMX devices at the same time

    3. right, the max. OSCin frequency is 100MHz in Cat.3 sync. Timing between OSCin and SYNC signal are also important.

    Your circuit will work as long as the timing requirement above is met.

  • 0 in reply to Noel Fung
    Intellectual 865 points

    Hi Noel,

    Thank you very much for your timely reply.

    And I have another question,why the Oscin frequency is 100M max in Cat.3 SYNC? Does this mean that the Fpfd can not be high, which will affect the near end phase noise.Or i can enable OSCin Doubler here?

    BR

  • 0 in reply to user5959213
    TI__Guru* 88940 points

    Hi Hips,

    In below timing spec, min. setup time is 9ns, this sets the max. OSCin frequency in Cat. 3 SYNC.