Digital-type delay locked loop with expanded input locking range

Abstract

A low-jitter delay locked loop having an expanded phase locking range without the necessity of setting the initial delay is provided. The loop is to be supplied by a system clock and includes a pulse generator receiving the system clock for generating a first pulse signal and a second pulse signal in response to a triggering signal, a delay device receiving the system clock for providing a delayed clock in response to a control signal, a frequency-reducing device for frequency-reducing the system clock into a first clock in response to the first pulse signal and frequency-reducing the delayed clock into a second clock in response to the second pulse signal, and a comparator for comparing the first and second clocks to generate the control signal.