Patent ID: 8462885
Filing Date: 2013-06-11
Classification: H03L

Abstract:
1. A phase-locked loop circuit for obtaining an output signal having an output frequency obtained by multiplying a frequency of a reference signal by an arbitrary integer X of 1 or greater and having a phase synchronized with that of the reference signal, comprising: a reference signal source configured to generate the reference signal having cycles; a voltage-controlled oscillator configured to generate a first signal and a second signal having a phase reverse to that of the first signal, frequencies of the first signal and the second signal being controlled depending on a control voltage; a phase comparator configured to acquire a first sampled voltage by sampling a voltage of the first signal in each cycle of the reference signal; a first charge pump configured to generate a current signal depending on the first sampled voltage; a loop filter configured to generate the control voltage to be supplied to the voltage-controlled oscillator by smoothing the current signal; a switch configured to have an ON state and an OFF state and supply the current signal generated by the first charge pump to the loop filter in the ON state and to block the supply of the current signal to the loop filter in the OFF state; a counter configured to count a cycle number of the second signal included in one cycle period of the reference signal; a second charge pump configured to supply, to the loop filter, a first current signal having a constant value and a second current signal having a constant value whose polarity is reverse to that of the first current signal, and selectively has any one of a first state for supplying only the first current signal, a second state for supplying only the second current signal, and a third state for not supplying either of the first current signal and the second current signal; and a control circuit configured to control the switch and the second charge pump based on a comparison between the cycle number of the second signal counted by the counter and the value X.