A Multichannel Wireless sEMG Sensor Endowing a $0.13 \ \mu \mathrm{m}$ CMOS Mixed-Signal SoC

This paper presents a wireless multichannel surface electromyography (sEMG) sensor which features a custom 0.13- $\mu \mathrm{m}$ CMOS mixed-signal system-on-chip (SoC) analog frontend circuit. The proposed sensor includes 10 sEMG recording channels with tunable bandwidth (BW) and analog-to-digital converter (ADC) resolution. The SoC includes 10x bioamplifiers, $10\mathrm{x}3^{rd}$ order $\Delta \Sigma$ MASH 1-1-1 ADC, and 10x on-chip decimation filters (DF). This SoC provides the sEMG samples data through a serial peripheral interface (SPI) bus to a microcontroller unit (MCU) that then transfers the data to a wireless transceiver. We report sEMG waveforms acquired using a custom multichannel electrode module, and a comparison with a commercial grade system. Results show that the proposed integrated wireless SoC-based system compares well with the commercial grade sEMG recording system. The sensor has an input-referred noise of $2.5 \ \mu \mathbf{V}_{rms}$ (BW of 10–500 Hz), an input-dynamic range of 6 $\mathbf{mV}_{pp}$, a programmable sampling rate of 2 ksps, for sEMG, while consuming only $7.1 \ \mu \mathrm{W}/\mathrm{Ch}$ for the SoC (w/ ADC & DF) and 21.8 mW of power for the sensor (Transceiver, MCU, etc.). The system lies on a $1.5 \ \mathrm{x}\ 2.0\ \mathrm{cm}^{2}$ printed circuit board and weights $< 1\mathrm{g}$.