Patent ID: 6664861
Filing Date: 2003-12-16
Classification: H03L

Abstract:
A phase-locked loop apparatus, comprising:a comparator configured to compare phases of a reference clock signal and an output signal of said apparatus and to output a voltage in accordance with a difference in phase as a comparison result; a filter configured to integrate the voltage output from said comparator; a voltage-controlled oscillator configured to control a frequency of an output signal in accordance with the voltage output from said filter, said voltage-controlled oscillator comprising: a ring oscillator configured to include a delay circuit including a plurality of inverters connected in a ring form; a plurality of first transistors corresponding to said plurality of inverters of said ring oscillator on a one-to-one basis and configured to control a current supplied by a first power source voltage to a positive side power source terminal of each of said plurality of inverters; a plurality of second transistors corresponding to said plurality of inverters of said ring oscillator on a one-to-one basis and configured to control a current output from a negative side power source terminal of each of said plurality of inverters; a voltage-to-current converter configured to convert said voltage output from said filter into a current; a first current mirror circuit configured to output a current in accordance with the current output from said voltage-to-current converter; a second current mirror circuit configured to output a current in accordance with the current output from said first current mirror circuit to a control signal input terminal of each of said plurality of first transistors; and a third current mirror circuit configured to output a current in accordance with the current output from said second current mirror circuit to a control signal input terminal of each of said plurality of second transistors, wherein said voltage-to-current converter, said first and second current mirror circuits operate with a second power source voltage greater than the first power source voltage, and said ring oscillator and said third current mirror circuit operate with said first power source voltage.