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|A 0.18μm CMOS Analog Front-End IC for Gas Sensors|
|Keywords: Sensor, Readout IC, platform|
|An electrochemical sensor readout analog front-end (AFE) IC for recording long term chemical and gas exposure is presented. The AFE readout circuit enables the detection of exhaust fumes in hazardous diesel and gasoline equipment, which helps correlate atmospheric pollutants with severe illnesses. The AFE reads out the output of eight conductometric sensor arrays and eight amperometric sensor arrays. The IC consists of a low noise potentiostat and associated 9 bits current-steering DAC for sensor stimulus, followed by the first order nested chopped ΣΔ ADC. The conductometric sensor uses a current driven approach for extracting resistance change of the sensor depending on gas concentration. The amperometric sensor uses a potentiostat to apply constant voltage for measuring current out of the sensor after a chemical reaction. The core area for the AFE is 2.65x0.95 mm2. The IC is fabricated in 0.18μm CMOS process and achieves 91dB SNR with 1.32mW power consumption per channel from a 1.8 V supply. With digital offset storage and nested chopping, the readout IC achieves 500 μV input referred offset. In order to use the system with AFE as part of a compact badge with battery, the entire gas detection system has been designed in 3D layers with a bio sensor mounted layer, an AFE layer, power management layer, a micro controller layer, and battery.|
|Hyuntae Kim, Student
Arizona State University