Clock synchronizing circuit

摘要

A clock synchronizing circuit provides reduced power consumption. A first phase comparator compares an external clock signal delayed for a predertermined time with a feedback clock signal to detect their phase error, and a second phase comparator compares an external clock signal with a feedback clock signal delayed for a predetermined time to detect their phase error. A charge pump changes a charge amount depending on phase error detecting signals from the first and second phase error comparators, and a phase compensator compensates the phase of the external clock signal depending on the charge amount from the charge pump. A controller controls the overall system or some portion thereof to be converted to a power save mode if the phase of the external clock signal is synchronized with that of the feedback clock signal by the phase compensator.