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how to confirm the PLL is locked?

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icfb

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how to confirm the PLL is locked by the signals of "UP" and "DOWN"

thank you
 

You have several choices. One is that the up and down times are a small fraction of a period. Another is to integrate the two with a short time constant and look for a constant voltage not at either end of the range. (Vcc or ground)
 

Hi icfb,

Look here, it's a small lock detector circuit that I found in the application
notes of the 1975 RCA COS/MOS Integrated Circuits databook.



If it doesn't work, it's their fault, not mine. :D

on1aag.
 

Hi,

Also the control voltage of the VCO should be a constant value in the range of the required control at lock.

Regards,
Shohdy
 

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