Patent ID: 6643317
Filing Date: 2003-11-04
Classification: H04B

Abstract:
A spread spectrum circuit for generating a clock output signal with reduced amplitude electromagnetic interference (EMI) spectral components, said spread spectrum circuit comprising:a clock pulse generator for generating a primary clock signal having a fundamental frequency with a fundamental amplitude, wherein said primary clock signal is comprised of a series of clock pulses and wherein said clock pulses are composed of a plurality of spectral components at differing frequencies, said primary clock signal also having fundamental EMI spectral components at harmonics of said fundamental frequency, said fundamental EMI spectral components each having a fundamental amplitude; a delay for delaying transmission of said primary clock signal; a selector for selecting from a plurality of available clock signals; a controller for driving said selector; a combiner for combining a selected first clock signal with a selected second clock signal to generate an output clock signal having combined characteristics of said first clock signal and said second clock signal; and an aggregator cooperating with said selector and said combiner for generating a spread spectrum clock output signal having a nominal frequency substantially equivalent to said fundamental frequency of said primary clock signal, wherein said nominal frequency includes nominal EMI spectral components at harmonics of said nominal frequency, said nominal EMI spectral components each having a nominal amplitude, and wherein said nominal amplitude is less than said fundamental amplitude.