Dual-mode wide-range linear CMOS interface circuit for resistive sensors

Abstract

A dual-mode adaptive method to provide a wide-range linear sensing characteristic over various resistive sensors is presented. A high-R mode acts as a resistance-to-digital converter without an analogue-to-digital converter (ADC), and a low-R mode utilises an adaptive current source to keep the required ADC resolution below 8 bits. A prototype of the dual-mode sensor interface was fabricated in a 0.18 mu m CMOS process, and its measured coverage of sensor resistance was from 750 to 1.2 MO. The power dissipation with a 1.8 V supply was 2.6-3.1 mu W in the high-R mode and 0.31-2.1 mW in the low-R mode.