| 摘要 |
PROBLEM TO BE SOLVED: To provide a PLL circuit having a function of an oscillation stop detection circuit for detecting that the oscillation of a voltage-controlled oscillator is stopped when a phase comparator input signal maintains a voltage that is nearly of VDD or VSS longer than the specified time. SOLUTION: The PLL circuit includes: the oscillation stop detection circuit 15 for detecting that the oscillation of the voltage-controlled oscillator 13 is stopped on the basis of a comparator input signal after frequency-dividing the oscillation signal of the voltage-controlled oscillator 13 including a ring oscillator wherein an odd number of inverters are connected in a ring; and a gate voltage adjustment circuit 16 for the voltage-controlled oscillator 13 that adjusts an input voltage to the voltage-controlled oscillator 13 on the basis of an oscillation stop signal from the oscillation stop detection circuit 15 so as to control the ring oscillator to normally oscillate. COPYRIGHT: (C)2004,JPO&NCIPI
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