| 摘要 |
PURPOSE:To shorten phase locking time by supplying a bias voltage to the output terminal of a loop filter before an external clock signal is supplied, and preventing a charge pump circuit from being operated. CONSTITUTION:A bias voltage supply circuit B is provided at the output terminal of the loop filter 3, and when a voltage of low level is supplied to a switch signal 11 before the external clock signal 6 is inputted, voltages in which a power supply voltage is voltage-divided by the on-resistance of transistors(TR) 12, 13 are outputted, which charge the capacitance C of the loop filter 3 in a moment. Thereby, a control voltage added on the input terminal of a voltage controlled oscillation circuit 4 is increased, in a moment, and the oscillation frequency of the circuit 4 can also rise in a short time. After that, an operation is performed by supplying the external clock signal 6. Also, when the bias voltage is supplied, waste current pass can be eliminated by preventing the charge pump circuit 2 from being operated by the input of a control signal 6. |
