| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a PLL circuit with a self-test function which can easily confirm the connection state of a circuit unit and a smoothing circuit which constitute the PLL. <P>SOLUTION: The PLL circuit is provided with a phase comparator 11 into which a signal oscillated by a VCO 17 and a reference signal are input, a charge pump 16 which elevates or downs output signal voltage of the phase comparator 11, and the smoothing circuit 30 which carries out smoothing of an output signal from the charge pump 16 to input to the VCO 17. The VCO 17 oscillates a signal which has nearly the same phase characteristic of the reference signal. The circuit unit 10 includes the phase comparator 11, the charge pump 15, and the VCO 17. The smoothing circuit 30 constituted as a separate body from the circuit unit 10 is electrically connected through a terminal P provided in the circuit unit 10. The circuit unit 10 includes a timing control circuit 13 which compulsorily charges and discharges a capacitor C composing the smoothing circuit 30, and a counter 12 which measures required time for completion of charging of the capacitor C of the smoothing circuit 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
