A semi-digital delay locked loop for clock skew minimization

A two-step approach for fast locking of a DLL (delay-locked-loop) circuit is discussed. The locking process consists of two steps; the coarse tuning in digital domain by tapping a delay position for fast coarse locking, and the accurate phase synchronization between the external clock and the internal clock in analog operation mode. With this two step approach, fast locking and low phase error can be simultaneously achieved.