A phase lock loop has a lock detection circuit, a phase comparator, a charge pump circuit, a low-pass filter, a variable delay circuit and a frequency divider. The lock detection circuit generates a lock detection signal when a phase difference between an input reference clock and an output of the variable...http://www.google.de/patents/US5629651?utm_source=gb-gplus-sharePatent US5629651 - Phase lock loop having a reduced synchronization transfer period
