99. A Multiplexed 20-Channel 6-Decade Range Resistance-to-Digital Converter for 2D Heterogeneous Metal-Oxide Gas-Sensor Arrays

The development and performance of a reconfigurable integrated read-out circuit for resistive heterogeneous 2D Metal-Oxide gas-sensor grids with local temperature control capability are reported. The MOX grid interface circuit is based on a resistance-to-frequency converter able to deliver up to 380 operating read-out configurations for a 5 × 5 sensing device. Temperature regulation of each row of the grid is provided thanks to independent sensor embedded platinum heaters and thermometers and separated control loops. The gas sensor front-end circuit prototype, developed in 0.35 μm technology with 3.3 V supply, features 170 dB dynamic range, while temperature regulation is guaranteed between ambient and 500 °C with an accuracy of 1 °C including residual dynamic ripple. To run a given sequence of measurements, reading-out digital output converted values, I²C serial interface is provided.