Patent ID: 7123102
Filing Date: 2006-10-17
Classification: H03L

Abstract:
1. A wireless communication semiconductor integrated circuit device that includes an oscillator capable of oscillations in a plurality of frequency bands, a variable frequency divider that divides a frequency of an output signal from the oscillator by a designated frequency dividing ratio, a fixed frequency divider that divides a predetermined frequency of a reference signal by a predetermined frequency dividing ratio, a phase comparator that compares a phase of an output signal from the variable frequency divider with a phase of an output signal from the fixed frequency divider to detect a difference between the phases, a loop filter that generates a voltage according to an output from the phase comparator, and a loop through which the voltage generated by the loop filter controls oscillation frequencies of the oscillator, the integrated circuit device comprising: switch means capable of supplying a predetermined potential to the oscillator as a control voltage with the loop open; a band selection circuit that compares the phase of the output signal from the variable frequency divider and the phase of the output signal from the fixed frequency divider in a state that the switch means supply the predetermined potential to the oscillator, and selects an oscillation frequency band of the oscillator; and a register that accepts, in order to prevent wrong selection of the oscillation frequency band due to a time lag in releasing the variable frequency divider and the fixed frequency divider from being reset, setting of a value by which another oscillation frequency band different from the selected oscillation frequency band is selected.