Patent ID: 8094698

Claim:
A method for generating a spread spectrum clock, comprising: providing a reference clock having a reference period; and generating the spread spectrum clock according to the reference clock, comprising the steps of: generating a plurality of output clocks respectively having different phases according to the reference clock; generating a first control signal according to the reference clock and the spread spectrum clock, and starting a first duration accordingly; during the first duration, outputting a first selecting signal representing a first predetermined sequence according to the first control signal; during the first duration, sequentially outputting some or all of the output clocks as the spread spectrum clock according to the first predetermined sequence of the first selecting signal; generating a second control signal according to the reference clock and the spread spectrum clock, and starting a second duration accordingly; during the second duration, outputting a second selecting signal representing a second predetermined sequence according to the second control signal, wherein the second predetermined sequence is a substantial reversed sequence of the first predetermined sequence; and during the second duration, sequentially outputting some or all of the output clocks as the spread spectrum clock according to the second predetermined sequence of the second selecting signal.