A small area fully integrated spread-spectrum clock generator with high EMI-reduction for SATA-3.0 applications

Abstract

In this paper, a small area spread-spectrum clock generator (SSCG) with high EMI reduction for SATA-3.0 is presented. Conventional methods use inductor-capacitance (LC) tank to fulfill the high frequency requirement for SATA-3.0. However, the monolithic inductors always occupy a large area, and required precisely characteristic for different fabrication processes. This research propose a SSCG using a ring voltage-controlled oscillators (Ring-VCO) at 6GHz operating frequency; By using the proposed Ring-VCO, the active area of SSCG is 65% of comparable LC tank implementations, and Ring-VCO is much easier to characterized for any CMOS process. In addition, a multi-stage-noise-shaping (MASH) delta-sigma modulator (ΔΣ modulator) is used to reduce fractional spurs and quantization error for high EMI reduction. The chip is designed in TSMC 0.18um 1P6M CMOS process with active area of 500um×300um, and the simulation results consumes 60.43mW with 1.8V supply. The peak-to-peak jitter at 6GHz output of non spread-spectrum is 6.16ps, and the EMI reduction is 22.49dB with 5000ppm down spread to 5.97GHz.