153dB dynamic range calibration-less gas sensor interface circuit with quasi-digital output

MOX gas sensors show a wide input resistance variation due to different employed materials, sensor ageing, and temperature variations, when encountering target gases. From the electronics point of view, a wide dynamic range readout interface is needed. The role of the interface is to accommodate the signal received by the sensor in order to be converted into digital or quasi-digital signal. This operation results to be very expensive in terms of calibration when exploiting a multi-scale approach (not satisfactory in terms of accuracy without calibration) or exploiting range compression either logarithmic or quadratic leading to unavoidable voltage drop. In this perspective, the paper presents the design of calibration-less, wide range readout electronic interface circuit with a quasi-digital output. The proposed resistance to time (R-to-T) architecture converts the wide resistance range (10k to 10G) into time with a relative linearity error lower than 1% and achieves a dynamic range of 153dB over 6-decades at transistor level simulations.