An EEG-NIRS Multimodal SoC for Accurate Anesthesia Depth Monitoring

Ha, Unsoo,Lee, Jaehyuk,Kim, Minseo,Roh, Taehwan,Choi, Sangsik,Yoo, Hoi-Jun IEEE 2018 IEEE journal of solid-state circuits Vol.53 No.6

<P>In surgical operation environments, anesthesia enables doctors to safe and accurate medical process with minimized movement and pain of patients. In general anesthesia, non-invasive and reliable monitoring of anesthesia depth is required because it is directly related to patient’s life. However, the current anesthesia depth monitoring approach, bispectral index (BIS), uses only electroencephalography (EEG) from the frontal lobe, and it shows critical limitations in the monitoring of anesthesia depth such as signal distortion due to electrocautery, electromyography (EMG) and dried gel, and false response to the special types of anesthetic drugs. In this paper, a multimodal head-patch system that simultaneously measures EEG and near-infrared spectroscopy (NIRS) on the frontal lobe is proposed. For EEG monitoring, mixed-mode dc-servo loop is proposed to cancel out the ±300-mV electrode-dc offset for dried gel condition with 3.59 noise-efficiency factor. To compensate the electromagnetic noises (EMG and electrocautery) in the system level, NIRS signal is measured. Logarithmic transimpedance amplifier (TIA) and closed-loop controlled (CLC) NIRS current driver are proposed. Logarithmic TIA can reject ambient light up to 10 nA to achieve a 60-dB dynamic range. According to the comparator output, CLC NIRS driver duty cycle can be adjusted from 0.625 m to 50 ms adaptively. The 16-mm<SUP>2</SUP> system-on-chip is fabricated in 65-nm CMOS. It dissipates 25.2-mW peak power. With the combined signals, it can show the clinically important transition from the awake to deep state, but BIS cannot detect the transition in a clinical trial.</P>

A 82-nW Chaotic Map True Random Number Generator Based on a Sub-Ranging SAR ADC

Minseo Kim,Unsoo Ha,Kyuho Jason Lee,Yongsu Lee,Hoi-Jun Yoo IEEE 2017 IEEE journal of solid-state circuits Vol.52 No.7

<P>An ultra-low power true random number generator (TRNG) based on a sub-ranging SAR analog-to-digital converter (ADC) is proposed. The proposed TRNG is composed of a coarse-SAR ADC with a low-power adaptive-reset comparator and a low-power dynamic amplifier. The coarse-ADC part is shared with a sub-ranging SAR ADC for area reduction. The shared coarse-ADC not only plays the role of discrete-time chaotic circuit but also reduces the overall SAR ADC energy consumption by selectively activating the fine-SAR ADC. Also, the proposed dynamic residue amplifier consumes only 48 nW and the adaptive-reset comparator generates a chaotic map with only 6-nW consumption. The proposed TRNG core occupies 0.0045 mm<SUP>2</SUP> in 0.18-μm CMOS technology and consumes 82 nW at 270-kbps throughput with 0.6-V supply. It successfully passes all of National Institute of Standards and Technology (NIST) tests, and it achieves the state-of-the-art figure-of-merit of 0.3 pJ/bit.</P>

An Impedance and Multi-Wavelength Near-Infrared Spectroscopy IC for Non-Invasive Blood Glucose Estimation

Kiseok Song,Unsoo Ha,Seongwook Park,Joonsung Bae,Hoi-Jun Yoo IEEE 2015 IEEE journal of solid-state circuits Vol.50 No.4

<P>A multi-modal spectroscopy IC combining impedance spectroscopy (IMPS) and multi-wavelength near-infrared spectroscopy (mNIRS) is proposed for high precision non-invasive glucose level estimation. A combination of IMPS and mNIRS can compensate for the glucose estimation error to improve its accuracy. The IMPS circuit measures dielectric characteristics of the tissue using the RLC resonant frequency and the resonant impedance to estimate the glucose level. To accurately find resonant frequency, a 2-step frequency sweep sinusoidal oscillator (FSSO) is proposed: 1) 8-level coarse frequency switching (f<SUB>STEP</SUB> = 9.4 kHz) in 10-76 kHz, and 2) fine analog frequency sweep in the range of 18.9 kHz. During the frequency sweep, the adaptive gain control loop stabilizes the output voltage swing (400 mV<SUB>p-p</SUB>). To improve accuracy of mNIRS, three wavelengths, 850 nm, 950 nm, and 1,300 nm, are used. For highly accurate glucose estimation, the measurement data of the IMPS and mNIRS are combined by an artificial neural network (ANN) in external DSP. The proposed ANN method reduces the mean absolute relative difference to 8.3% from 15% of IMPS, and 15-20% of mNIRS in 80-180 mg/dL blood glucose level. The proposed multi-modal spectroscopy IC occupies 12.5 mm 2 in a 0.18 μm 1P6M CMOS technology and dissipates a peak power of 38 mW with the maximum radiant emitting power of 12.1 mW.</P>

An 87-<tex> $\hbox{mA}\cdot \min$</tex> Iontophoresis Controller IC With Dual-Mode Impedance Sensor for Patch-Type Transdermal Drug Delivery System

Kiseok Song,Unsoo Ha,Jaehyuk Lee,Kyeongryeol Bong,Hoi-Jun Yoo IEEE 2014 IEEE journal of solid-state circuits Vol.49 No.1

<P>A bio-feedback iontophoresis controller IC is implemented into a fabric patch for transdermal drug delivery. An iontophoresis stimulator front-end (ISFE) can provide programmable stimulation current in the range of 16-512-μA amplitude, DC-500-Hz frequency, and 3% -100% duty cycle for controllable drug delivery. For safe and robust electrical stimulation, a failure detection circuit monitors the stimulation current to prevent overcurrent and stimulation voltage saturation. For bio-feedback operation, a dual-mode impedance sensor (DMIS) measures load and tissue impedances in the range of 5-50 kΩ and 5 Ω-1 kΩ, respectively. In the DMIS, the gain of a programmable gain amplifier and the injected current level of a chopper-modulated current source are automatically controlled to minimize power consumption. The proposed IC occupies 2.35 mm × 2.35 mm including pads in a 0.11-μm 1P6M CMOS technology and dissipates a peak power of 2.2 mW. The proposed IC is directly integrated on a 9 cm × 4 cm fabric circuit board together with a 6.2-mAh coin battery for convenient iontophoresis treatment. The proposed system provides a maximum dosage range of 87 mA·min, which is larger range than the 80- mA·min dosage range of a commercial iontophoresis patch. Using a reconfigurable tetra-polar electrode configuration, load and tissue impedances are measured during the iontophoresis treatment to provide bio-feedback. The proposed iontophoresis system is successfully verified by both in-vitro and in-vivo tests.</P>

0.025 mJ/image Fast-scan and SNR Enhanced Electrical Impedance Tomography IC for Lung Ventilation Monitoring

Jaehyuk Lee,Unsoo Ha,Hoi-Jun Yoo 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.6

Energy efficient lung monitoring electrical impedance tomography (EIT) IC is simulated in 180-nm CMOS process. To increase the speed of impedance sensing, fast settling high pass filter (FS-HPF) and fast settling low pass filter (FS-LPF) is proposed to reduce the settling time which takes over 90% of entire EIT data measurement latency. In FS-LPF, voltage-controlled pseudo-resistor is proposed to realize time-varying resistance. To reconstruct the accurate images, adaptive current control (ACC) scheme is implemented for SNR enhancement. Additional SNR improvements are accomplished by averaging the multiple measurements. As a result, image scanning speed of 30-fps is achieved with 0.025 mJ/Image energy efficiency. The simulation results show that ACC can reduce the image FOM error over 80% rather than conventional constant current injection method.

A 4.9 mΩ-Sensitivity Mobile Electrical Impedance Tomography IC for Early Breast-Cancer Detection System

Sunjoo Hong,Kwonjoon Lee,Unsoo Ha,Hyunki Kim,Yongsu Lee,Youchang Kim,Hoi-Jun Yoo IEEE 2015 IEEE journal of solid-state circuits Vol.50 No.1

<P>A mobile electrical impedance tomography (EIT) IC is proposed for early breast cancer detection personally at home. To assemble the entire system into a simple brassiere shape, EIT IC is integrated via a multi-layered fabric circuit board which includes 90 EIT electrodes and two reference electrodes for current stimulation and voltage sensing. The IC supports three operating modes; gain scanning, contact impedance monitoring, and EIT modes for the clear EIT image. A differential sinusoidal current stimulator (DSCS) is proposed for injection of low-distortion programmable current which has harmonics less than -59 dBc at a load impedance of 2 kΩ. To get high sensitivity, a 6-channel voltage sensing amplifier can adaptively control the gain up to a maximum of 60 dB, and has low input referred noise, 36 nV/ √Hz. The 2.5 × 5 mm chip is fabricated in a 0.18 μm 1P6M CMOS process and consumes 53.4 mW on average. As a result, a sensitivity of 4.9 mΩ is achieved which enables the detection of a 5 mm cancer mass within an agar test phantom.</P>