A 0.35 μm CMOS 17-bit@40-kS/s cascade 2-1 ΣΔ modulator with programmable gain and programmable chopper stabilization

Abstract

This paper describes a 0.35μm CMOS chopper-stabilized Switched-Capacitor 2-1 cascade ΣDelta; modulator for automotive sensor interfaces. For a better fitting to the characteristics of different sensor outputs, the modulator includes a programmable set of gains (x0.5, x1, x2, and x4) and a programmable set of chopper frequencies (fs/16, fs/8, fs/4 and fs/2). It has also been designed to operate within the restrictive environmental conditions of automotive electronics (-40°C, 175°C). The modulator architecture has been selected after an exhaustive comparison among multiple ΣΔM topologies in terms of resolution, speed and power dissipation. The design of the modulator building blocks is based upon a top-down CAD methodology which combines simulation and statistical optimization at different levels of the modulator hierarchy. The circuit is clocked at 5.12MHz and consumes, all together, 14.7mW from a single 3.3-V supply. Experimental measurements result in 99.77dB of Dynamic Range (DR), which combined with the gain programmability leads to an overall DR of 112dB. This puts the presented design beyond the state-of-the-art according with the existing bibliography.