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Original question:

LMK05028: The clock output frequency has frequency deviation

LMK05028: LMK05028 free-run tuning word

PHI TU
Prodigy 240 points
Part Number: LMK05028

Dear All

I'm using LMK05028 for lock 1PPS. I have a question about the "free-run tuning word"

As my understand the datasheet it will determine the initial holdover output frequency accuracy when When no tuning word history exists (Example input Ref lost during the history word average time). But i dont know how to calculate value of "free-run tuning word" (it is 38bit)

Best Regards,
Phi Tu

  • 0
    TI__Mastermind 28550 points

    Hello Phi,

    The free-run tuning word is a 2s compliment number which gets added to get numerator of the APLL when it goes into holdover.  If you simply leave the value at 0, then you will enter into holdover with the numerator of APLL.  When the APLL takes reference from XO, this means your output frequencies in holdover have the same frequency accuracy as the XO.

    73,
    Timothy