Delta-Sigma Modulation Sensor Interface Circuits with Improved Conversion Gain for Capacitive Readout Chemical Sensors

This paper presents improved capacitive readout type sensor interface circuits designed for CMOS integrated chemical sensors. The sensor is fabricated using a 0.8μm CMOS IC process technology. Volatile organic compounds (VOCs) are detected by measuring the capacitance change of polymer coated interdigital capacitors due to analyte absorption. The delta-sigma modulation sensor interface uses a sensor capacitor and a reference capacitor as those for the input of the frontend switched capacitor integrator. An improved capacitance sensing scheme is proposed to improve the sensitivity.