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Original question:

LMK05318B: Synchronizing GPS Clock with LMK05318B

LMK05318B: synchronization questions

nutt
Prodigy 20 points
Part Number: LMK05318B

Hi,

I have some questions about the synchronization capabilities of LMK05318B devices.

When I use the 1pps clock of GPS as a reference input, there are several questions that I don't understand all the time

1. OUT7 of 05318B has ZDM function, so only the phase of OUT7 can be consistent with the input PPS phase?

2. What is the relationship between the phase of out0~6 and the phase of PPS? What is the relationship with the phase of out7?

3. When I use the ZDM function to synchronize out7 to PPS, and then use the sync function to synchronize all output clocks, after synchronization, what is the phase relationship between out0~6 and out7?

4. Which reference is the sync synchronization function to synchronize the phase of each channel to? Can I synchronize the phase of out0~6 to out7?

  • 0
    TI__Guru* 81380 points

    Hi,

    Please allow some time for our experts to get back to you.

    Thanks.

  • 0 回复 Cherry Zhou
    TI__Guru* 81380 points

    Hi,

    1. Please note that the 5318B does not offer true ZDM mode because it uses a SYNC feature to get alignment between 1-PPS input and 1-PPS output. This means that the input to output phase relationship is not fixed across power cycles like with true ZDM. 
    2.  With the DPLL, the outputs will constantly get updated to be phase aligned with the PPS signal. This phase alignment means there could be a small phase offset between the input and the output (so if you connect the PRIREF/SECREF and OUTx to a scope, and zoom in on the edges, you may see the edges are not exactly on top of each other). However, the key is that all the outputs (0-7) will be phase/frequency synchronized to the PRIREF/SECREF input. 
    3. There may still be the phase offset between OUT0-6 against OUT7. For example, OUT7 may share same edge with PRIREF input and OUT0 to OUT6 could share the same edge but have a phase offset from PRIREF/OUT7.
    4. The key detail to find out is what kind of synchronization the customer wants. Must OUT0-7 share exactly the same phase/edge as PRIREF? Or is the concern to have OUT0-7 be phase/frequency synchronized to PRIREF/SECREF? If it's the second question, then the DPLL will handle this without SYNCing features. If it's the first, then this will be hard to do with LMK05318B if you want a 1-PPS output.

    Thanks.