| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a spread spectrum clock generator capable of obtaining ideal frequency characteristics without using a DAC having a large circuit scale and an analog modulation circuit, and a semiconductor device including the spread spectrum clock generator. <P>SOLUTION: The spread spectrum clock generator includes: a voltage-controlled oscillator generating an operation clock; a feedback controller comparing the phase of the operation clock and the phase of a reference clock and generating a voltage as the reference of the oscillation of the voltage-controlled oscillator on the basis of the results of the comparison; and a modulation pulse generator generating a component fluctuating the frequency of the operation clock as a pulse signal subjected to delta sigma modulation. The spread spectrum clock generator further includes: a level setter setting the amplitude of the pulse signal; an adder adding the voltage generated by the feedback controller and the pulse signal whose amplitude is set by the level setter; and a low-pass filter generating a control voltage to be applied to the voltage-controlled oscillator by filtering an output signal from the adder. <P>COPYRIGHT: (C)2011,JPO&INPIT |
