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LMX2594: SYNC pin timing in Category 3

Josh Merti
Prodigy 190 points
Part Number: LMX2594


I am trying to synchronize multiple LMX devices driven by the same, but possibly skewed, Fosc.  What method do you recommend using to distribute the SYNC pin signal and Fosc to guarantee the same Fosc cycle is selected by multiple LMX devices?  Is the SYNC pin latched on the next Fosc positive edge or is it acted upon immediately when the SYNC edge is detected?  How far from the previous positive Fosc edge does the SYNC signal need to be?

  • 0
    TI__Mastermind 28021 points
    Josh,

    The SYNC pulse waits til the next rising edge of Fosc and then this is when the actual synchronization is performed. So typically you might send SYNC pulse at the falling edge of Fosc and the skew would have to be pretty high to get the wrong edge. Datasheet specificies a 2.5 ns setup time and 2 ns hold time for this edge.

    Typically what is done for category 3 is to use a SYSREF output from another LMX or LMK device to generate the SYNC pulse such that it can be known for sure to be far away from any rising edges of Fosc.

    Regards,
    Dean