| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a voltage controlled oscillation circuit (VCO) which can adjust oscillation frequency without trimming, and a semiconductor integrated circuit for communication building in the oscillation circuit. <P>SOLUTION: A plurality of capacitor elements (C1 to C3) are connected in parallel using selecting means such as switches in the VCO circuit composing a PLL circuit. An LC resonance type oscillation circuit is used, which is configured to be possible to change oscillation frequency by changing constants (LC) of the circuit according to the selection state of the selection means. The VCO circuit comprises a comparator (50) which compares control voltage supplied from a loop filter of the PLL circuit to the VCO and standard voltage, and a frequency adjustment circuit (60) which generates a signal to control the selecting means based on the comparison result of the comparator. The VCO circuit is configured to decide the signal for control the selection means by the successive comparison. <P>COPYRIGHT: (C)2004,JPO |
