Lock detection circuit for phase locked loop

Details Lock detection circuit for phase locked loop Lock detection circuit for phase locked loop

2009-04-02

2011-12-13

Kinkead, Arnold (Department: 2817)

Oscillators

Automatic frequency stabilization using a phase or frequency...

Afc with logic elements

C331S00100A, C331S017000, C331S025000, C331S027000, C331SDIG002, C327S003000, C327S007000, C327S040000, C327S047000, C327S048000, C327S156000, C327S160000

Reexamination Certificate

active

08076979

ABSTRACT:
A lock detector circuit for detecting a lock condition between a reference signal and a feedback signal includes a first counter for outputting a first counter value indicative of a number of clock cycles of the reference signal, and a second counter for outputting a second counter value indicative of a number of clock cycles of the feedback signal. An asynchronous comparator receives the first and second counter values and provides an output signal having a pulse width that is proportional to the difference between the first and second counter values. A pulse width detector receives the comparator output signal and produces an output signal that is indicative of the relationship between the pulse width of the comparator output signal and a predetermined threshold value. A state machine controls the state of at least one lock indication signal according to the pulse width detector output signal.

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