Patent ID: 6677788
Filing Date: 2004-01-13
Classification: H03C,H03L

Abstract:
A semiconductor integrated circuit comprising:a voltage controlled oscillator; a phase comparator for comparing a phase of an oscillation output of the voltage controlled oscillator with a phase of a reference clock signal; and a control voltage generating circuit for generating a voltage which eliminates a phase difference detected by the phase comparator and applying the voltage as a first control voltage to said voltage controlled oscillator, said voltage controlled oscillator, said phase comparator, and said control voltage generating circuit constructing a phase locked loop, said voltage controlled oscillator being controlled by said first control voltage to generate a frequency signal as a reference, and data transmission being performed while changing the frequency by controlling said voltage controlled oscillator with a second control voltage based on transmission data, wherein when a frequency modulating operation is performed with said second control voltage, said phase locked loop is set in an open state, and wherein a temperature characteristic correcting circuit is included, which gives a temperature characteristic inverse to a temperature characteristic of said voltage controlled oscillator to said second control voltage.