This paper presents an integrated circuit solution for multi-channel neuromuscular electrical stimulation (NMES). The stimulation waveform is digitally controlled and supports monophasic pulses, and both symmetric and asymmetric biphasic pulses. In addition, the current intensity is programmable, ranging from 0 mA to 31 mA with 5-bit resolution. The integrated circuit occupies an area of 1 mm2and it is designed and simulated in a 180 nm high-voltage CMOS technology. The circuits are powered using standard 1.8 V and 3.3 V power supplies for the digital control and digital-to-analog converter, and a single 40 V power supply for the output drivers. The simulation results show that the design achieves a voltage compliance of up to 35 V, meeting the requirements for NMES applications while offering a very compact and scalable solution.

This brief presents an integrated solution to over-current protection in neuromuscular stimulators. The proposed approach provides fast detection of a single-fault condition, i.e., unintentional electrode short circuit or malfunction of the stimulator, thereby preventing prolonged high-intensity currents from flowing into tissues. In addition, a programmable current threshold enables the system to be also used for monitoring the stimulation intensity. The proposed solution was designed in a 180 nm high-voltage CMOS technology, and its functionality was verified by post-layout simulations in which the safety mechanisms were tested under fault conditions. The implementation only occupies an area of 0.286 mm2, making it feasible to be embedded in fully integrated NMES stimulators while providing the required patient safety.

Neuromuscular electrical stimulation (NMES) requires voltages exceeding several tens of volts which are typically obtained by using DC-DC boost converters. However, these converters incorporate a large external inductor, which hinders integration and severely restricts the minimum size of the stimulator. This paper presents a charge pump (CP) high-voltage generator particularly designed for NMES applications. The proposed hybrid CP comprises a low-voltage latched CP followed by a high-voltage Dickson CP with boosted pumping clocks. This architecture generates an output voltage of 40.5 V from a 3.3 V supply, enabling the delivery of up to 30 mA stimulation pulses at a maximum frequency of 50 Hz. The circuit is designed in a 180 nm HV CMOS process and occupies a silicon area of 2.7 mm 2 . By eliminating the inductor and requiring only one external storage capacitor, this design has the potential of being used in compact stimulators for wearable medical applications.

Biopotential acquisition chopper instrumentation amplifiers require a dc-servo loop (DSL) in order to filter electrode dc offsets. However, the noise performance degradation due to the addition of the DSL is often overlooked despite that it can be very detrimental at the frequencies of interest. This article presents an in-depth noise analysis of biopotential acquisition chopper instrumentation amplifiers with analog DSLs. Analytical expressions that predict the noise of different DSL implementations are found and a design flow to minimize their noise contribution is proposed. The design methodology is demonstrated with example circuits targeting biopotential recording systems. These circuits are implemented using a standard 180 nm CMOS technology, and their performance is verified through postlayout simulations. The findings of this work provide a comprehensive understanding of the noise characteristics of a DSL, its impact on noise performance, and design strategies for noise optimization.

This paper presents a 16-channel analog frontend (AFE) for wearable multi-channel surface electromyographyrecording. The proposed architecture adopts frequency-divisionmultiplexing (FDM), enabling extensive sharing of signal conditioning circuitry and requiring only three cables for transmissionto an external back-end for digital signal processing. Benefitingfrom the up-conversion process, the FDM signal exhibits robustness against cable motion artifacts and mains interference,allowing short-distance communication without compromisingsignal quality. This work achieves a channel-to-cable ratio of16:3, dramatically reducing system complexity. Implemented ina 180 nm CMOS technology, the proposed 16-channel AFEoccupies only 6.42 mm2and consumes 40.1 µW per channelfrom a 1.5 V supply. Measurements on a forearm demonstratethe capability to simultaneously detect muscle activation fromvarious muscle groups, showcasing its potential for gesturerecognition applications.

Neuromuscular electrical stimulation (NMES) is a self-directed home based therapeutic tool in early rehabilitation for musculoskeletal (MSK) conditions. However, the effectiveness of traditional NMES is fundamentally constrained by muscle fatigue. To address this limitation, this work proposes a detection system, which simultaneously records multifrequency electrical impedance myography (EIM) and surface electromyography(sEMG) in real time for time-frequency analysis of muscle activation, contraction, and fatigue. To demonstrate the ability to monitor these muscle physiological states, two experiments involving weightless and weighted dynamic contractions of the biceps brachii muscle were performed. Results from these experiments show synchronous changes in sEMG and EIM spectra during contractions, and clear trends in sEMG’s mean power frequency (MPF) and EIM spectra with fatigue progression. Additionally, the configurable 4-channel NMES has been electrically evaluated for clinical use, demonstrating the feasibility of the proposed system for closed-loop stimulation. This work showcases the potential of sEMG and multi-frequency EIM to enhance the effectiveness of NMES for MSK conditions by capturing the behavior of distinct mechanisms of muscle fatigue.