| 摘要 |
PURPOSE:To easily realize an externally synchronizing system with a small number of parts by inputting both external and internal signals to a phase comparator in order to produce the signals showing the gain or the loss of phases the external and internal signals. CONSTITUTION:A voltage control oscillation circuit 6 produces a signal S3 having an oscillation frequency fZ corresponding to the voltage of a signal S0 outputted from a low pass filter 5. A 1/N frequency dividing circuit 1a divides the signal S3 down to 1/N and outputs an internal signal S2. A phase comparator 3 detects the difference of phases between both signals S1 and S2, and a signal corresponding to the phase difference is outputted from a charge pump circuit 4. Furthermore the signal S0 integrated by the filter 5 is outputted. This feedback control is automatically repeated so that the phase difference between the external signal S1 and the internal signal S2 is set at zero and the external synchronization is attained to the signal S1. Thus it is possible to easily obtain an externally synchronizing system with a small number of parts. |
