Semiconductor integrated circuit for communication

A semiconductor integrated circuit for communication comprising:

• a loop that includes:
• an oscillation circuit constructed to be able to oscillate in plural frequency bands;
• a variable frequency divider that frequency-divides an output signal of the oscillation circuit at a specified frequency division ratio;
• a fixed frequency divider that frequency-divides a reference signal having a predetermined frequency at a predetermined frequency division ratio;
• a phase comparison circuit that compares the phase of an output signal of the variable frequency divider and the phase of an output signal of the fixed frequency divider to detect a phase difference;
• a loop filter that generates a control voltage corresponding to the output of the phase comparison circuit, and controls oscillation frequencies of the variable oscillation circuit by a control voltage generated by the loop filter;
• a switching means that can supply a voltage of a predetermined level to the loop filter in place of the output of the phase comparison circuit when the loop is open;
• and
• a band switching circuit that, in a state of supplying a control voltage of the predetermined level to the oscillation circuit by supplying the voltage of the predetermined level to the loop filter by the switching means, compares the phase of an output signal of the variable frequency divider and the phase of an output signal of the fixed frequency divider to select an oscillation frequency band of the oscillation circuit,
• wherein, after applying a control voltage of a first predetermined level to the oscillation circuit by the switching means, and selecting a frequency band by the band switching circuit, the semiconductor integrated circuit for communication applies a control voltage of a predetermined level different from the first predetermined level, and decides in which region on a line of control voltage to oscillation frequency characteristics the oscillation circuit is operating, based on a comparison result of the phase comparison circuit.