A 1.5 mm2 4-Channel EEG/BIOZ Acquisition ASIC with 15.2-bit 3-step ADC based on a signal-dependent low-power strategy

This paper presents a multichannel EEG/BIOZ acquisition application specific integrated circuit (ASIC) with 4 EEG channels and a BIOZ channel. Each EEG channel includes a frontend, a switch resistor low-pass filter (SR-LPF), and a 4-channel multiplexed analog-to-digital converter (ADC), while the BIOZ channel features a pseudo sine current generator and a pair of readout paths with multiplexed SR-LPF and ADC. The ASIC is designed for size and power minimization, utilizing a 3-step ADC with a novel signal-dependent low power strategy. The proposed ADC operates at a sampling rate of 1600 S/s with a resolution of 15.2 bits, occupying only 0.093mm 2 . With the help of the proposed signal-dependent low-power strategy, the ADC's power dissipation drops from 32.2μW to 26.4μW, resulting in an 18% efficiency improvement without performance degradation. Moreover, the EEG channels deliver excellent noise performance with a NEF of 7.56 and 27.8 nV/√Hz at the expense of 0.16 mm 2 per channel. In BIOZ measurement, a 5-bit programmable current source is used to generate pseudo sine injection current ranging from 0 to 22μApp, and the detection sensitivity reaches 2.4mΩ/√Hz. Finally, the presented multichannel EEG/BIOZ acquisition ASIC has a compact active area of 1.5 mm 2 in an 180nm CMOS technology.