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

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 μm CMOS process, and its measured coverage of sensor resistance was from 750 to 1.2 MΩ. The power dissipation with a 1.8 V supply was 2.6–3.1 μW in the high‐ R mode and 0.31–2.1 mW in the low‐ R mode.