An EEG-NIRS ear-module SoC for wearable drowsiness monitoring system

An electroencephalogram (EEG) - near-infrared spectroscopy (NIRS) ear-module SoC is proposed for the non-intrusive wearable drowsiness monitoring system. The proposed SoC is integrated into earpiece-type system with ear hook and it can show the driver drowsiness states with multimodal measurement. It has 3 key building blocks; 1) multi-dimensional compensation transimpedance amplifier with ambient current rejection of 0.1-12.8nA and extra-cerebral current rejection of 0.2-4nA for world-first ear-NIRS. 2) SNR-optimizing VCSEL driver for minimizing driving current with 7 bit DAC 3) reconfigurable impedance boosting loop for the input impedance > 5GΩ As a result, it shows over 60% accuracy to classify the 3 missed stimuli on Oxford Sleep Resistance Test. The proposed ear-module SoC of 0.45 × 2.25mm² is fabricated in 0.11 μm CMOS technology. It dissipates 14mA in the worst case with duty-cycling.