PHASE LOCK DETECTION CIRCUIT ADOPTING WINDOW METHOD TO DETECT PHASE LOCK SAFELY

摘要

PURPOSE: A phase lock detection circuit is provided to output a hysteresis phase lock detection signal robust to noises and to detect the phase lock safely by using a window method. CONSTITUTION: A phase lock detection circuit includes a phase lock detector(101) and a lock detection control block(103). The phase lock detector(101) uses a window method to determine lock statuses of a reference clock and a lock clock. The lock detection control block(103) includes an internal digital counter and programs threshold values according to transition types of an N-bit digital input from outside. The programmable phase lock detection circuit uses an output of the phase lock detector(101) to increase or decrease the counter, and compares the counted result with a threshold value inputted from outside according to a current on-lock or off-lock status to determine a final on-lock or off-lock status.