| 摘要 |
PROBLEM TO BE SOLVED: To provide a signal supply circuit in which the accuracy and stability of the frequency of an output clock can be prevented from decreasing significantly, by generating a preliminary clock signal that can be changed over upon occurrence of nonsteady state of an external clock signal.SOLUTION: A signal supply circuit includes a changeover section 10 supplied with a first frequency signal (preliminary clock signal 150), and a second frequency signal (external clock signal 110), and capable of changing over the out put from the second frequency signal to first frequency signal, a comparison section 20 for controlling the first frequency signal by a first signal (signal Vc1) based on a first control signal (signal CMP) comparing the phase of the first and second frequency signals, a nonsteady detector 30 for detecting nonsteady of the second frequency signal, and generating a second signal (nonsteady detection signal ERR) depending on the presence and absence of nonsteady of the second frequency signal, and a control section 40 for controlling the first frequency signal by a second control signal based on the first control signal before indicating nonsteady, when the second frequency signal is nonsteady. |
