A $\Delta\Sigma$ Modulator-Based Spread-Spectrum Clock Generator with Digital Compensation and Calibration for Phase-Locked Loop Bandwidth

Abstract

A spread-spectrum clock generator (SSCG) is an essential building block for reducing electromagnetic interference (EMI) in a system-on-a-chip without shielding the device that increases the system cost and weight. In a ${\Delta } {\Sigma }$ modulator (DSM)-based SSCG, EMI reduction is degraded by attenuating the harmonic components of the generated profile owing to the phase-locked loop bandwidth ( $ {f}_{{\text {LBW}}}$ ). This brief proposes a DSM-based SSCG with a digital compensator to maximize EMI reduction with a triangular profile. By adaptively reconfiguring the gains of the digital compensator, the proposed SSCG maintains the EMI reduction regardless of $ {f}_{\text {LBW}}$ variations. The EMI reduction is improved by 2.17 dB at 1.35 GHz with the lowest $ {f}_{\text {LBW}}$ . A prototype of the proposed SSCG is fabricated using 65-nm CMOS technology. The measured RMS jitter and power consumption are is 2.47 ps and 7 mW, respectively and the die occupies 0.292 mm2.