A 32-/22W 1.83-kS/s Carbon Nanotube Chemical Sensor System Taeg Sang Cho, Student Member , IEEE, Kyeong-Jae Lee , Student Member , IEEE

Abstract

This paper presents an energy-efficient chemical sensor system that uses carbon nanotubes (CNT) as the sensing medium. The room-temperature operation of CNT sensors elim- inates the need for micro hot-plate arrays, which enables the low energy operation of the system. An array of redundant CNT sen- sors overcomes the reliability issues incurred by the CNT process variation. The sensor interface chip is designed to accomodate a 16-bit dynamic range by adaptively controlling an 8-bit DAC and a 10-bit ADC. A discrete optimization methodology determines the dynamic range of the DAC and the ADC to minimize the energy consumption of the system. A simple calibration technique using off-chip reference resistors reduces the DAC non-linearity. The sensor interface chip is designed in a 0.18- m CMOS process and consumes, at maximum, 32 /87at 1.83 kS/s conversion rate. The designed interface achieves 1.34% measurement accuracy across the 10 k /10–9 M/10range. The functionality of the full system, including CNT sensors, has been successfully demonstrated.