| 摘要 |
PROBLEM TO BE SOLVED: To provide a fractional N-PLL circuit, etc. that can properly set the operation range of a voltage-controlled oscillation circuit without excessively increasing the frequency at which delta sigma modulation is performed.SOLUTION: A fractional N-PLL circuit 20 has a voltage-controlled oscillation circuit 24 capable of setting plural output frequency ranges for a control voltage range, a frequency selection circuit 26 for searching plural output frequency ranges of the voltage-controlled oscillation circuit 24 and selecting one output frequency range, a frequency dividing circuit 25 provided on a signal path from the output of the voltage-controlled oscillation circuit 24 to the input of the voltage-controlled oscillation circuit 24, and a divided frequency setting circuit 27 for performing delta signal modulation to set a frequency division ratio of the frequency dividing circuit 25. The divided frequency setting circuit 27 performs delta signal modulation at a frequency lower than the frequency after the frequency selection circuit 26 finishes the search while the frequency selection circuit 26 is searching the plural output frequency ranges of the voltage-controlled oscillation circuit 24.SELECTED DRAWING: Figure 2 |
