An 0.18μm CMOS electrochemical sensor readout IC for exhaust gas monitoring

A fully integrated 8-channel gas readout analog front-end IC is presented. The IC enables detection and identification of harmful environmental pollutants in exhaust gas fumes for extended periods, which in turn helps with correlating different pollutants with several illnesses. The system can read out an array of eight conductometric and amperometric electrochemical sensors while multiplexing analog-front-end circuitry to reduce die size. The IC consists of a low noise front-end and low DC offset, multiplexed ADC. The conductometric sensor uses a novel current steering approach for extracting impedance of the sensor. To reduce 1/f noise and DC offset voltage, a nested-chopper stabilized ADC is used. The detection analog front-end achieves 67.2 dB SNR at 1.57 mW quiescent power consumption per channel, enabling a chemical detection sensitivity of 1ppm in volume.