US 6,982,707 B2
Method and apparatus utilizing direct digital synthesizer and spread spectrum techniques for reducing EMI in digital display devices
Vincent Wang, San Jose, Calif. (US)
Assigned to Genesis Microchip Inc., Alviso, Calif. (US)
Filed on Dec. 18, 2002, as Appl. No. 10/323,557.
Claims priority of provisional application 60/364981, filed on Mar. 14, 2002.
Prior Publication US 2003/0174126 A1, Sep. 18, 2003
Int. Cl. G09G 5/00 (2006.01)
U.S. Cl. 345—213 16 Claims
OG exemplary drawing
 
1. A clock synthesizer circuit arranged to provide a selectable spread spectrum based output clock signal, comprising:
a phase accumulator;
a reference clock source coupled to the phase accumulator circuit arranged to provide a reference clock signal;
an adder unit coupled to the phase accumulator;
a nominal phase source coupled to the adder unit arranged to provide a nominal phase signal; and
a modulated phase source coupled to the adder unit arranged to provide a phase modulation signal, wherein the adder unit combines the nominal phase signal and the phase modulation signal to form a frequency shift signal as input to the phase accumulator that uses the frequency shift signal to sample the reference clock signal so as to produce the output clock signal having a central frequency about the same as the reference clock signal and an associated frequency spread based on the phase modulation signal.