Patent ID: 7242916
Filing Date: 2007-07-10
Classification: H03L

Abstract:
1. A semiconductor integrated circuit device for a wireless communication system, comprising: an oscillation means for generating an oscillation signal having an oscillation frequency in accordance with frequency instruction information, including: a phase detection circuit which detects a phase difference between a reference signal of a predetermined frequency and a feedback signal; a charge pump circuit for generating a first voltage in response to the phase difference detected by the phase detection circuit; and an oscillation circuit for oscillating on the basis of a second voltage of a filter capacitor charged/discharged by the charge pump circuit; a storing means for storing measured frequency information of the oscillation circuit; a frequency band determination means for comparing the measured frequency information stored with the frequency instruction information, and generating a signal for determining an oscillation frequency band of the oscillation circuit; a voltage generation means for generating a third voltage applied to the filter capacitor or the oscillation circuit on the basis of the measured frequency information adapted to an oscillation frequency band determined by the frequency band determination means stored in the storing means and the frequency instruction information; a switching means for subjectively supplying the first voltage according to an output of the charge pump circuit or the third voltage generated by the voltage generation means as a control voltage of the oscillation circuit; and a control means for controlling the switching means, wherein the third voltage generated by the voltage generation means is supplied as an initial voltage to either the filter capacitor or the oscillation circuit by the switching means to perform a sink operation at start of operation of the oscillation means, and the switching means is switched to supply the control voltage according to an output of the charge pump circuit to the oscillation circuit to set the oscillation frequency of the oscillation means.