Patent ID: 8040191
Filing Date: 2011-10-18
Classification: H03L

Abstract:
1. A PLL circuit comprising: first and second charge pump circuits that control an output voltage according to an output signal of a phase comparator; a first filter that filters out a predetermined frequency component included in a signal generated according to a current output from the first charge pump circuit, and outputs the signal as a first voltage signal; a second filter that inputs a current output from the second charge pump circuit and outputs a predetermined constant voltage as a second voltage signal; a voltage control unit that outputs a third voltage signal according to a comparison result between the first voltage signal and a reference voltage signal, the first voltage signal being output from the first filter; and a voltage controlled oscillator that has a first low gain property, a second low gain property, and a high gain property, and is controlled by the first voltage signal with the first low gain property, by the second voltage signal with the second low gain property, and by the third voltage signal with the high gain property, to generate an oscillating frequency according to the first to third voltage signals, wherein the PLL circuit feeds back an output signal of the voltage controlled oscillator to the phase comparator.