Patent ID: 6949958
Filing Date: 2005-09-27
Classification: G06F,H03L,H04L

Abstract:
1. A phase comparator for use in conjunction with a clock domain crossing circuit, comprising: a first sampling circuit for sampling a first clock with a first edge of second clock to produce a selection signal, wherein the first and second clocks are mesochronous; a second sampling circuit for sampling a third clock having a fixed phase differential relative to the first clock to produce a first sample signal, the third clock being sampled with a second edge of the second clock, the second edge of the second clock having an opposite transition direction relative to the first edge of the second clock; a third sampling circuit for sampling the third clock with the first edge of the second clock to produce a second sample signal; and a multiplexer for selectly outputting one of the first and second sample signals in accordance with the selection signal to produce a phase comparison signal, wherein the phase comparison signal has a value that is determined by a phase difference between the first clock and the second clock.