3 GHz Spread Spectrum Clock Generator for Serial ATA-II using Random Frequency Modulation

This paper proposes a Spread Spectrum Clock Generator specifically meant for 3 GHz Serial ATA-II applications. The spreading is obtained through a PLL frequency modulation driven by a random signal, to avoid strict periodicity of the clock and thus high peaks in its power spectral density. The circuit, including a PLL-modulator and a Random Bit Generator has been designed in UMC 0.18 um technology; the random bit generator is based on a chaotic-map. Simulations show Electromagnetic Compatibility improvement of approximately 13 dB with respect to the reference case. A prototype of this circuit is currently under fabrication.