1.9-ps Jitter, 10.0-dBm-EMI Reduction Spread-Spectrum Clock Generator With Autocalibration VCO Technique for Serial-ATA Application

A spread-spectrum clock generator (SSCG) that is characterized by a low jitter voltage-controlled oscillator (VCO) with a high-frequency limiter and an autocalibration function is developed for a Serial-ATA application. The high-frequency limiter prevents the SSCG from going into an unlocked state. The proposed VCO achieved far less jitter than a conventional one because a proposed structure has fewer operating MOSs that are noise sources. The autocalibration technique calibrates the VCO sensitivity, the maximum frequency of the VCO output signal, and the characteristics of the limit function to prevent the SSCG from degrading an output jitter and an electromagnetic interference (EMI) reduction due to a process variation. The proposed SSCG with the autocalibration function was fabricated in a 0.13-μm CMOS process. The variation in the jitter in 250-cycles at 1.5 GHz with spread-spectrum clocking (SSC) is improved from 2.1-7.8 ps to 1.9-3.3 ps and the EMI reduction is achieved as 10.0 dBm by the proposed autocalibration technique.