Delay-locked loop (DLL) integrated circuits that support...

Details Delay-locked loop (DLL) integrated circuits that support... Delay-locked loop (DLL) integrated circuits that support...

2006-09-19

2006-09-19

Le, Dinh T. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By phase

C327S003000, C327S007000

Reexamination Certificate

active

07109760

ABSTRACT:
Delay-locked loop (DLL) integrated circuits include digital phase comparators that are unaffected by variable duty cycle ratios. These phase comparators determine a shortest direction to phase lock before establishing a value of a compare signal (COMP) that specifies the shortest direction. The phase comparator is responsive to a reference clock signal REF and a feedback clock signal FB. These clock signals have equivalent periods and may have equivalent non-unity duty cycle ratios. The phase comparator is configured to determine whether a first degree to which the reference clock signal REF leads the feedback clock signal FB is smaller or larger than a second degree to which the reference clock signal REF lags the feedback clock signal FB. Based on this determination, the phase comparator generates a compare signal COMP that identifies a direction in time the feedback clock signal FB should be shifted to bring it into alignment with the reference clock signal REF. This direction represents a speed-up direction when the first degree is determined to be less than the second degree or a slow-down direction when the second degree is determined to be less than the first degree.

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