A High-Resolution Interface Circuit based on Resistance-to-Frequency Conversion for Resistive Gas Sensor

• Published in: 2021 IEEE 4th Advanced Information Management, Communicates, Electronic and Automation Control Conference (IMCEC) Vol. 4; pp. 486 - 491
• Main Authors: Qi, Weijie, Li, Chunling, Wang, Jing, Gu, Wenxian, Chen, Dongliang, Adedokun, George, Xu, Lei
• Format: Conference Proceeding
• Language: English
• Published: IEEE 18.06.2021
• Subjects: Correlation coefficient; Ethanol; Frequency measurement; high resolution; interface circuit; Power supplies; Resistance; resistance-to-frequency conversion; resistive gas sensor; Semiconductor device measurement; Voltage measurement
• ISSN: 2693-2776
• DOI: 10.1109/IMCEC51613.2021.9482052

In this paper, a high-resolution interface circuit for resistive gas sensor is proposed. The circuit is based on resistance-to-frequency conversion which uses a buffer to keep the voltage across the gas sensor unchanged in order to eliminate the influence of voltage change on sensing material. The circuit has been fabricated in a 0.18 um CMOS technology with 1.8 V power supply. The area of the chip including PAD is only 640 um × 550 um. The experimental results report that the Pearson Correlation Coefficient is 0.99998 between the period of output signal and resistance when the measured resistance range is 500 Ω to 10 MΩ with corresponding signal frequency range of 1.23 MHz to 137 Hz. The interface circuit can detect the minimum change of 1 Ω resistance at a measured resistance of 500 Ω and 8.5 KΩ resistance at a measured resistance of 10 MΩ. For static gas, the chip can detect the ethanol gas concentration of 0 to 200 ppm and can detect a gas concentration change of 20 ppb at a low concentration.