The DLL comprises a coarse delay line configured to have a plurality of unit delays and delay an reference dock to output a delayed clock, a fine delay line configured to delay the delayed clock to output a delayed output clock, a replica delay unit configured to delay the delayed output clock by an expected modeling value to output a feedback clock, a phase detection unit configured to compare a phase of the feedback clock with a phase of the reference clock to generate first to third phase detection signals based on a result of the comparison, a locking detection unit configured to output a locking signal by selecting a first locking detection signal or a second locking detection signal, and a control unit configured to control the coarse and fine delay lines in response to the locking signal and the first phase detection signal.