Digital phase comparator without dead zone

摘要

A digital phase comparator comprises a first signal input (VCO) and second signal input (REF) as well as a first output (UP+) and second output (DOWN+). It is arranged so as to produce an output pulse (503, 504) to the first output and second output per each of the cycles of the periodic signals (501, 502) brought to the first signal input and second signal input. The duration of the output pulse produced to the first output is longer than the duration of the output pulse produced to the second output when the phase of the periodic signal brought to the first signal input is lagging with respect to the phase of the periodic signal brought to the second signal input. Correspondingly, the duration of the output pulse produced to the first output is shorter than the duration of the output pulse produced to the second output when the phase of the periodic signal brought to the first signal input is leading with respect to the phase of the periodic signal brought to the second signal input. The phase comparator is arranged so as to make the starting times of the output pulses produced to the first output and second output substantially simultaneous.