| 摘要 |
PURPOSE:To realize accurately the detection of a phase locking or a pseudo locking by sampling a count value of a 1st counter circuit with a signal obtained through the comparison between an output of a square sum circuit and a prescribed value so as to quicken phase locking. CONSTITUTION:When phase synchronization is established, a phase of an output pulse of a 1st comparator circuit 12a is the same as a phase of a carry of a 1st counter circuit 11a, and when the count value is sampled by an output of a 1st comparator circuit 12a, the sampled value is '0'. Thus, a 2nd comparator circuit 12b compares the reference value '0' with an output of a 4th S/H circuit 7d and provides an output of a pulse indicating phase locking when they are coincident. Then a protection circuit 13a discriminates the establishment of phase locking when a prescribed number of output pulses of the 2nd comparator circuit 12b is counted. The signal changes from an H level to an L level when the phase locking is established, for example and changes from an L level to an H level when run-locking is settled and whether or not the phase locking is established is discriminated by extracting the level change externally. |
