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  • 1.
    Fernández Schrunder, Alejandro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Huang, Yu-Kai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    A Bioimpedance Spectroscopy Interface for EIM Based on IF-Sampling and Pseudo 2-Path SC Bandpass ΔΣ ADC2024In: IEEE Transactions on Biomedical Circuits and Systems, ISSN 1932-4545, E-ISSN 1940-9990, p. 1-13Article in journal (Refereed)
    Abstract [en]

    This paper presents a low-noise bioimpedance (bio-Z) spectroscopy interface for electrical impedance myography (EIM) over the 1 kHz to 2 MHz frequency range. The proposed interface employs a sinusoidal signal generator based on direct-digital-synthesis (DDS) to improve the accuracy of the bio-Z reading, and a quadrature low-intermediate frequency (IF) readout to achieve a good noise-to-power efficiency and the required data throughput to detect muscle contractions. The readout is able to measure baseline and time-varying bio-Z by employing robust and power-efficient low-gain IAs and sixth-order single-bit bandpass (BP) ΔΣ ADCs. The proposed bio-Z spectroscopy interface is implemented in a 180 nm CMOS process, consumes 344.3 - 479.3 μ W, and occupies 5.4 mm 2 area. Measurement results show 0.7 mΩ/√Hz sensitivity at 15.625 kHz, 105.8 dB SNR within 4 Hz bandwidth, and a 146.5 dB figure-of-merit. Additionally, recording of EIM in time and frequency domain during contractions of the bicep brachii muscle demonstrates the potential of the proposed bio-Z interface for wearable EIM systems.

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  • 2.
    Huang, Yu-Kai
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    An Inductorless 40.5V High-Voltage Generator for Integrated Neuromuscular Electrical Stimulators2023In: Proceedings 2023 IEEE Biomedical Circuits and Systems Conference (BioCAS), Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper (Refereed)
    Abstract [en]

    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.

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  • 3.
    Huang, Yu-Kai
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Noise Analysis and Design Methodology of Chopper Amplifiers With Analog DC-Servo Loop for Biopotential Acquisition Applications2023In: IEEE Transactions on Very Large Scale Integration (vlsi) Systems, ISSN 1063-8210, E-ISSN 1557-9999, p. 1-13Article in journal (Refereed)
    Abstract [en]

    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.

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  • 4.
    Huang, Yu-Kai
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Noise Analysis of Current-Feedback DC-Servo Loop in Current-Balancing Chopper Amplifiers2022In: 2022 IEEE NORDIC CIRCUITS AND SYSTEMS CONFERENCE (NORCAS) / [ed] Nurmi, J Wisland, DT Aunet, S Kjelgaard, K, Institute of Electrical and Electronics Engineers (IEEE) , 2022Conference paper (Refereed)
    Abstract [en]

    Chopper amplifiers for biopotential acquisition commonly suppress differential electrode DC offsets by using a DC-servo loop (DSL). However, the noise contribution of the DSL is always neglected in noise analysis. The noise introduced by the DSL, in particular at low frequencies, is of great importance in biosensor applications. This work presents the noise modeling of a current-balancing chopper amplifier with DSL and describes the effect of the DSL on the noise performance. Two different DSL implementations are analyzed. It is found that the exact placement of the chopper in the DSL has a strong impact in the noise performance; therefore, its placement can not be arbitrarily selected. A circuit topology to minimize its noise contribution is then proposed and verified by simulation.

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  • 5.
    Huang, Yu-Kai
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    A 4-Channel NMES IC for Wearable Applications2021In: BioCAS 2021 - IEEE Biomedical Circuits and Systems Conference, Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2021Conference paper (Refereed)
    Abstract [en]

    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.

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  • 6.
    Huang, Yu-Kai
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    A Current Monitoring and Over-Current Detection Circuit for Safe Electrical Stimulation2023In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 70, no 5, p. 1684-1688Article in journal (Refereed)
    Abstract [en]

    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.

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1 - 6 of 6
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