A Low-Pass Filter Bandwidth Adaptation Technique for Phase Interpolators

Abstract

This paper presents a technique to automatically adapt the bandwidth of the low-pass filter (LPF) of the phase interpolator (PI) used in bang-bang clock and data recovery (CDR) circuits. A technique for introducing the reference nonlinearity in the presence of PI’s nonlinearity is presented. This reference is used for LPF bandwidth adaptation. A mathematical model for the PI nonlinearity and introduction of reference nonlinearity is proposed. Using this model, analysis and design of the proposed bandwidth adaptation are done. The technique is verified by simulations and Si-measurements using a full-rate bang-bang CDR, which is fabricated in 180-nm CMOS technology. The PI occupies an area of 0.014 mm2 and consumes 1.1 mA for 1-GHz PI clock frequency while working on 1.8-V supply.