Unsoo Ha

18.4 A 4.9mΩ-sensitivity mobile electrical impedance tomography IC for early breast-cancer detection system

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.

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

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 (fSTEP = 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 mVp-p). 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.

A Wearable EEG-HEG-HRV Multimodal System With Simultaneous Monitoring of tES for Mental Health Management

A multimodal mental management system in the shape of the wearable headband and earplugs is proposed to monitor electroencephalography (EEG), hemoencephalography (HEG) and heart rate variability (HRV) for accurate mental health monitoring. It enables simultaneous transcranial electrical stimulation (tES) together with real-time monitoring. The total weight of the proposed system is less than 200 g. The multi-loop low-noise amplifier (MLLNA) achieves over 130 dB CMRR for EEG sensing and the capacitive correlated-double sampling transimpedance amplifier (CCTIA) has low-noise characteristics for HEG and HRV sensing. Measured three-physiology domains such as neural, vascular and autonomic domain signals are combined with canonical correlation analysis (CCA) and temporal kernel canonical correlation analysis (tkCCA) algorithm to find the neural-vascular-autonomic coupling. It supports highly accurate classification with the 19% maximum improvement with multimodal monitoring. For the multi-channel stimulation functionality, after-effects maximization monitoring and sympathetic nerve disorder monitoring, the stimulator is designed as reconfigurable. The 3.37 × 2.25 mm 2 chip has 2-channel EEG sensor front-end, 2-channel NIRS sensor front-end, NIRS current driver to drive dual-wavelength VCSEL and 6-b DAC current source for tES mode. It dissipates 24 mW with 2 mA stimulation current and 5 mA NIRS driver current.

An impedance and multi-wavelength near-infrared spectroscopy IC for non-invasive blood glucose estimation

A multi-modal spectroscopy IC combining the impedance spectroscopy (IMPS) and the multi-wavelength near-infrared spectroscopy (mNIRS) is proposed for high precision non-invasive glucose level estimation. A frequency sweep (10kHz - 76kHz) sinusoidal oscillator (FSSO) is proposed for high resolution (500 steps) for IMPS. The output voltage swing of the FSSO is stabilized by an adaptive gain control (AGC). The measurement results of the IMPS and mNIRS are combined by an artificial neural network (ANN) in external smart device so that mean absolute relative difference (mARD) is enhanced to 8.3% from 15% of IMPS, 15% - 20% of mNIRS. A proposed 12.5mm2 0.18μm CMOS chip consumes peak power of 38mW at 1.5V.

18.5 A 2.14mW EEG neuro-feedback processor with transcranial electrical stimulation for mental-health management

Recently, mental diseases have been successfully treated by neuro-feedback therapy based on Quantitative EEG (QEEG) and Event Related Potential (ERP) online data measurements. The U.S. Food and Drug Administration (FDA) approved the first EEG test for diagnosing attention deficit hyperactivity disorder (ADHD) in 2013 [1]. The EEG signals are measured by an EEG cap and analyzed by a high performance computer to extract not only the EEG power at a predetermined frequency and site combinations, but also the degree of coherence between all sites. Based on these results, brain stimulation is performed to modulate brain rhythms (EEG) toward the normal values for the therapy.

An 87-

In this paper, we present an iontophoresis controller IC with real-time monitoring of total injected charge quantity and skin condition. The proposed IC contains 32-level programmable current stimulator, a temperature sensor and a dual impedance sensor to monitor skin temperature, contact and tissue impedances. The measured temperature and impedances, related with the skin condition, are used for adaptive charge injection by modifying the current stimulation levels through the real-time feedback path. An implemented fabric patch type drug delivery system provides up to 87mA-min dosage larger than the dosage range (80mA-min) of commercial iontophoresis patches [4].

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An ultra-low power true random number generator (TRNG) based on sub-ranging SAR ADC is proposed. The proposed TRNG shares the coarse-ADC circuit with sub-ranging SAR ADC for area reduction. The shared coarse-ADC not only plays the role of discrete-time chaotic circuit or TRNGs entropy source but also reduces overall SAR ADC energy consumption by selectively activating the fine-SAR ADC. Also, the proposed dynamic residue amplifier and adaptive-reset comparator generate chaotic map with low power consumption. TRNG core occupies 0.0045mm2 in 0.18μm CMOS technology and consumes 82nW at 270kbps throughput with 0.6V supply. The proposed TRNG passes all NIST tests and it achieves a state-of-the-art FOM of 0.3pJ/bit.

Iontophoresis Controller IC With Dual-Mode Impedance Sensor for Patch-Type Transdermal Drug Delivery System

A low-power electrical impedance tomography (EIT) IC proposed for breast cancer diagnosis is implemented in 180nm CMOS process. For the breast cancer diagnosis, low power and high accuracy is required. The proposed IC reduces the power consumption to 3.8mW using the homodyne conversion mixer to lower the sampling rate of ADC. To gain high accuracy, the adaptive filter using the miller capacitor perfectly filters out the ECG signal. I/Q dual path architecture measures conductivity and permittivity components separately, so distance errors are reduced about 86% in simulation.

A 82nW chaotic-map true random number generator based on sub-ranging SAR ADC

A closed-loop electroencephalogram (EEG) — near-infrared spectroscopy (NIRS) ear-module system for wearable drowsiness system is proposed. It is implemented on the earpiece and ear hook. Thanks to the ear-module SoC in the earpiece, the proposed system monitors 1-ch EEG and 1-ch NIRS simultaneously with small form-factor. Since the NIRS signal can be easily distorted because of ambient light and extra-cerebral artifact, dedicated noise reduction scheme is proposed for ear-NIRS. After the measured physiology signal is transferred to MCU in the ear hook, it is preprocessed and classified. With the classified result, alarm makes user feel awake. The proposed system is fully implemented and verified by Oxford Sleep Resistance Test. It shows the improved classification accuracy up to 20%. As a result, the proposed system is expected to be effectively utilized for closed-loop drowsiness monitoring with the multimodal signal monitoring and auditory alarm as well as convenient and non-intrusive form factor. It has only 40g weight and operates at least 5 hours with 3.6V 200mAh rechargeable battery.

3.8 mW electrocardiogram (ECG) filtered electrical impedance tomography IC using I/Q homodyne architecture for breast cancer diagnosis

In this paper, a power-efficient equalization techniques is proposed for a high data-rate multi-standard wireline receiver. First, a low-frequency-equalizing continuous-time linear equalizer (LFE-CTLE) compensates for not only the short-term inter-symbol interference (ISI) from high-frequency channel loss but also the long-term ISI from the low-frequency channel loss without additional power consumption compared to the previous CTLE. LFE-CTLE can reduce the required number of taps and power consumption of the following decision feedback equalizer (DFE). A 2-tap speculative DFE adopts 4-phase clocking techniques to reduce the number of summation nodes and latches for low-power consumption. The proposed receiver is designed in 65-nm LP CMOS technology with 1.-2V supply voltage. It can achieve 28-Gb/s data rate with a 24-mW power efficiency.