Phase-locked loop circuit

Details Phase-locked loop circuit Phase-locked loop circuit

1998-10-19

2000-07-25

Callahan, Timothy P.

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Synchronizing

327158, 327159, 327157, H03L 706

Patent

active

060940786

ABSTRACT:
A PLL circuit taking a shorter time to accomplish phase locking with reduced jitter is provided. A phase/frequency detector circuit section includes: a first phase/frequency detector having phase/frequency difference detection characteristic substantially free from a dead zone; and a second phase/frequency detector having phase/frequency difference detection characteristic with a dead zone of a predetermined width. If the phase/frequency difference between a reference signal and a signal to be compared is too small to be detected by the second phase/frequency detector, only the first phase/frequency detector detects the phase/frequency difference. On the other hand, if the phase/frequency difference between the reference signal and the signal to be compared is sufficiently large, then both the first and second phase/frequency detectors detect phase/frequency difference. Thus, if the phase/frequency difference between the reference signal and the signal to be compared is large, a large amount of current is supplied from a charging pump circuit section to a low-pass filter. Conversely, if the phase/frequency difference is small, a small amount of current is supplied from the charging pump circuit to the low-pass filter.

REFERENCES:
patent: 4322643 (1982-03-01), Preslar
patent: 4612515 (1986-09-01), Ohkawa et al.
patent: 5095287 (1992-03-01), Irwin
patent: 5550515 (1996-08-01), Liang

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