A 124 dB dynamic range sigma-delta modulator applied to non-invasive EEG acquisition using chopper-modulated input-scaling-down technique

• Published in: Science China. Information sciences Vol. 65; no. 4; p. 140402
• Main Authors: Chen, Kaiquan, Chen, Mingyi, Cheng, Longlong, Qi, Liang, Wang, Guoxing, Lian, Yong
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01.04.2022; Springer Nature B.V
• Subjects: Analog to digital converters; Computer Science; Dynamic range; Electroencephalography; Figure of merit; Human-computer interface; Information Systems and Communication Service; Low noise; Power consumption; Research Paper; Signal to noise ratio; brain computer interface (BCI); motion artifacts (MA); ΣΔ modulator; analog-to-digital converter (ADC); dynamic range (DR); electroencephalogram (EEG)
• ISSN: 1674-733X; 1869-1919
• DOI: 10.1007/s11432-021-3401-6

With the advancement of brain science in recent years, the non-invasive brain-computer interfaces (BCIs) based on electroencephalogram (EEG) acquisition have been widely adopted in various brain-inspired applications. The acquisition of multi-channel microvolts EEG signals corrupted by the motion artifacts (MAs) of up to several volts poses enormous challenges to the design of analog front-end (AFE), especially the analog-to-digital converter (ADC), which is necessary to achieve low noise, wide dynamic range (DR), high accuracy as well as low power. In this paper, a wide DR ΣΔ modulator with chopper-modulated input-scaling-down (CM-ISD) technique has been proposed to deal with large input offset while extending dynamic range. Fabricated in 180 nm CMOS technology, the prototype occupies a core area of 0.32 mm 2 . With a 40 Hz input signal and 125 Hz Nyquist bandwidth, the measured signal-to-noise ratio (SNR) and signal-to-noise and distortion ratio (SNDR) are 117 and 110 dB, respectively. Thanks to the proposed CM-ISD technique, the modulator is capable of withstanding a full-scale (4.5 V pp ) input whereas the measured DR has been extended from 99 to 124 dB. The power consumption is 2.75 mW under 5 V supply voltage, corresponding to 170.6 dB Schreier figure-of-merit (FoM S ). The multi-channel EEG acquisition has been demonstrated based on the proposed modulator, showing its potential in advanced non-invasive BCI systems.