Semiconductor device for clock signals synchronization accuracy

摘要

A semiconductor device that generates a clock which is synchronized with a reference signal stably and with fixed synchronization accuracy, and enables to deal with an abrupt variation in the reference signal. This semiconductor device includes N stages of delay elements each delaying an external clock by 1/N clock (N: an integer that is two or larger); a phase comparator for comparing the phase of a clock that has been delayed by the N stages of the delay elements with the phase of the external clock one clock late; a controller that receives a phase difference detected by the phase comparator and controls respective delays of the delay elements; and a selector for selecting a delayed clock having the closest phase to the reference signal from delayed clocks which are generated by the N stages of the delay elements, respectively, and shifted in phase with each other by 1/N clock.