Phase frequency detector having reduced blind spot

Details Phase frequency detector having reduced blind spot Phase frequency detector having reduced blind spot

1997-12-19

1999-10-05

Callahan, Timothy P.

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By phase

327 7, 331 1A, 331 25, H03D 320, H03D 1300

Patent

active

059630590

ABSTRACT:
A phase-frequency detector provides a decreased blind spot near 360.degree. of phase error and a resulting increased phase error detection range. In one embodiment, the phase-frequency detector includes two latches that are set in response to the detection of positive transitions in respective input clock signals. A reset controller resets both latches when they both get set. The duration and sequence of the latch states are thereby indicative of phase errors between the input clock signals. Two edge-triggered pulse generators provide a sustained indication of a detected positive transition in the respective input clock signals. When the time duration of the sustained indications is set equal to the reset time required by the latches and reset controller, the blind spot of the phase-frequency detector is largely eliminated.

REFERENCES:
patent: 5172397 (1992-12-01), Llewellyn
patent: 5271040 (1993-12-01), Clark
patent: 5319680 (1994-06-01), Port et al.
patent: 5699387 (1997-12-01), Seto et al.
patent: 5736872 (1998-04-01), Sharma et al.
Von Kaenel, et al., "A 320MHz, 1.5mW at 1.35V CMOS PLL for Microprocessor Clock Generation," ISSCC96/Session 8/Digital Clocks and Latches/Paper FA 8.2, pp. 132-133.
"5.2 Phase and Frequency Detectors," Tutorial, Pre-1997, pp. 21-26.

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