Anti-deadlock circuit and method for phase-locked loops

Details Anti-deadlock circuit and method for phase-locked loops Anti-deadlock circuit and method for phase-locked loops

2005-02-08

2005-02-08

Pascal, Robert (Department: 2817)

Oscillators

Automatic frequency stabilization using a phase or frequency...

Tuning compensation

C331S025000

Reexamination Certificate

active

06853254

ABSTRACT:
A system and method for controlling a phase-locked loop detects a deadlock condition and then adjusts an output frequency of an oscillator until the deadlock condition is corrected. The deadlock condition may be detected based on a value of a charge pump signal which controls the oscillator frequency. In accordance with one embodiment, deadlock is detected if the value of the charge pump signal approaches one of two supply rail voltages. The deadlock condition is overcome by manipulating current signals output from the charge pump. This is accomplished by turning off the current from one charge-pump current source and increasing current from a second-charge pump current source. The increased current may be provided by a third current source located within or external to the charge pump. By adding current from the third current source, the output frequency of the phase-locked loop will be driven lower until a value is reached which effectively pulls the PLL out of the deadlock condition.

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patent: 20010013801 (2001-08-01), Johnson

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