| 摘要 |
PROBLEM TO BE SOLVED: To reduce adverse effects due to electromagnetic interference EMI by reducing EMI peak energy. SOLUTION: A loop filter LF that extracts a DC component and a low-frequency component from the output of a phase frequency comparator circuit provided for an input of a voltage-controlled oscillator VCO of this PLL circuit consists of resistors R1, R2 and a capacitor C. A control signal applied to the voltage-controlled oscillator VCO is changed by giving a fluctuation modulated signal, whose frequency is lower than that of a clock signal outputted from the voltage controlled oscillator VCO, to a node A so as cause a clock signal outputted by the voltage controlled oscillator VCO to fluctuate. Thus, the spectrum is spread and reduce the EMI peak energy is reduced. |
