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 |
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.
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