A Chemoresistive Gas Sensor Readout Integrated Circuit with Sensor Offset Cancellation Technique

This study proposes a chemoresistive gas sensor readout integrated circuit (ROIC) with a simple and effective scheme for tracking and canceling the sensor offset value. Before reading out the gas sensor, the proposed ROIC dynamically updates a of analog-to-digital (A/D) reference range suitable to the gas sensor offset, enabling accurate A/D conversion within the gas sensor's dynamic range (DR). Therefore, this approach eliminates the need for additional complex circuitry or compensation algorithms, allowing the ROIC to extract the desired amount of change effectively. As a result, the overall DR of the gas sensor system is maximized. In addition, the proposed ROIC maintains compatibility with the existing system environment while effectively alleviating the physical limitations of the gas sensor. In terms of commercialization, the effectiveness and feasibility of the proposed ROIC, based on a single-slope A/D converter structure as a readout technique, have been verified. A prototype ROIC was fabricated employing a 180-nm standard CMOS process, exhibiting a total power consumption of 0.5 mW with a conversion rate of 62.5 kSPS. The integrated noise within the range of 1 Hz to 2 kHz was 10.1 μ VRMS , corresponding to a DR of 137 dB. Further, the maximum integral non-linearity (INL) was -72.24 dB. The proposed ROIC effectively minimizes sensor offset scattering within 1 LSB of the A/D reference full scale, enhancing performance and feasibility in gas sensor applications.