Uses the phase simulation circuit and the said phase simulation circuit the phase simulation manner

摘要

PROBLEM TO BE SOLVED: To establish a synchronization state in a short time by using a clock error detection circuit and a control voltage comparator circuit so as to detect whether an input clock is normal or in error. ;SOLUTION: A VCO control voltage outputted from a phase comparator circuit 11 is given to an LPF 12, in which a high frequency component is eliminated and the resulting voltage is outputted as a control voltage (a). The control voltage (a) is given to an A/D converter circuit 13 and a selection circuit 16. A clock error detection circuit 19 detects a state of an input clock and gives the error detection signal to a memory circuit 14 and the selection circuit 16. When it is discriminated that the input clock restores from the erroneous state to the normal state, a control voltage (b) outputted from the A/D converter circuit 13 is compared with a control voltage (c) outputted from the memory circuit 14 by a control voltage comparator circuit 20. When they are not equal to each other, a phase of an output clock from a VCO 17 controlled by a control voltage (d) is controlled by a frequency divider circuit 18.;COPYRIGHT: (C)1997,JPO