A 141-dB Dynamic Range CMOS Gas-Sensor Interface Circuit Without Calibration With 16-Bit Digital

Abstract

In this paper, we present the design and the charac- terization of a wide-dynamic-range interface circuit for resistive gas-sensors able to operate without calibration. The circuit is based on resistance-to-frequency conversion, which guarantees low complexity. The state-of-the-art of this measurement method has been improved first by separating the Resistance value Con- trolled Oscillator circuit (RCO) from the sensing device, thus leading to higher linearity performance, and then by exploiting a novel digital frequency measurement system. Measurement results on a silicon prototype, designed in a 0.35- m CMOS technology, show that the circuit achieves, without calibration, a precision in resistance measurement of 0.4% over a range of 4 decades and better than 0.8% over 5 decades (dynamic range, DR /61141 dB). Furthermore, after calibration, it reaches a precision of 0.4% for resistance values ranging between 1 k /10and 1 G /10, thus leading to a DR of 168 dB. The prototype chip consumes less than 15 mW from a 3.3-V supply.