AXIS — Analog X Integrated Systems · Gachon University

ANALOG X
INTEGRATED SYSTEMS

The AXIS Design Laboratory — a central axis in analog and mixed-signal integrated circuits.

We build versatile integrated circuits and systems that push performance and efficiency, spanning precision analog circuits, data converters, power management ICs, and circuits for AI systems.

Explore research Join the lab

Precision Analog Data Converters PMIC / Energy Harvesting In-Sensor Computing Edge AI

Mission

Precise, efficient, compact, robust.
On every axis.

AXIS builds versatile integrated circuits and systems — precision analog front-ends, high-resolution data converters, power management ICs, and circuits for AI systems. The X in our name is a variable: the application changes, the standards do not — accuracy, energy efficiency, compact integration, and robustness in the field.

01 Research

What we work on

AXIS advances mixed-signal integrated circuits for ultra-low-power, high-accuracy sensor interfaces, power management and energy harvesting, data converters, and edge-AI / in-sensor computing. Our mission rests on four axes: accuracy that holds over time and temperature, system-level energy efficiency, compact integration, and robustness in real-world deployment.

Theme · PMIC / EH 01

Power Management & Energy Harvesting ICs

Our PMIC research enables battery-constrained or battery-free operation in distributed sensors and edge devices. We study autonomous start-up, adaptive power-tracking algorithms, and multi-mode DC–DC conversion with integrated protection and safety. We also develop on-chip regulation using low-dropout regulators (LDOs) and precision references (bandgap references, BGRs), and investigate power delivery for AI servers and HBM stacks.

FocusStart-up for energy-scarce sources · maximum-power-tracking control · mode-transition efficiency · on-chip regulation (LDOs) · precision references (BGRs) · AI-server / HBM power delivery.

Theme · AFE 02

Precision Analog & Sensor Interfaces

We design low-power, low-drift analog front-ends for environmental, industrial, and biomedical sensing. Emphasis is placed on accuracy over temperature and lifetime, input stages tailored to each sensor's source characteristics, and robustness to interference.

FocusPrecision amplification · source-matched readout · calibration and system-level linearity.

Theme · ADC / DAC 03

Data Converters (ADC / DAC)

We develop energy-efficient data converters tailored to sensing and instrumentation. Architectures are chosen per application to achieve high effective resolution at low supply voltages, and are co-optimized with analog front-ends and digital post-processing.

FocusConverter-system co-design · dynamic-range management · background calibration · verification from behavioral models to silicon.

Theme · ISC / Edge 04

In-Sensor Computing & Edge AI

We explore near-sensor analog pre-processing and low-overhead feature extraction to reduce data movement and energy. Designs are co-optimized with the sensing modality and the downstream digital pipeline.

FocusAnalog-domain preprocessing · event-driven capture · standardized interfaces for photonic, resistive, and capacitive sensors.

02 Selected Works

Publications

28 journal & conference papers · * Corresponding author

2026

IEEE Sensors J.S. Han, H. Eom, K. Du, H. Lee, N. Kim, J. Rhee*

A One-Port Floating-Target Capacitance-to-Digital Converter with Consecutive Double-Sided Conversion and Extended Counting ADC Achieving 157.5 aFrms at 316-pF Input Capacitance

IEEE Sensors Journal, 2026

IEEE TCAS-IIJ. Yun, J. Rhee*

A Fully Integrated 16-MHz Voltage-Mode Relaxation Oscillator with Current Calibration for Temperature Compensation

IEEE Trans. Circuits & Systems II: Express Briefs, vol. 73, no. 4, Apr. 2026

IEEE TVLSICH. Kye, D. Yun, J. Han, M. Park, K. Kim, K. Back, E. Lee, WS. Choi, DK. Jeong, J. Rhee*

A 48-Gb/s PAM-4 Transceiver With Transition Boosting and RLM Calibration for Next-Generation Memory Interface Testing

IEEE Trans. Very Large Scale Integration (VLSI) Systems, vol. 34, no. 3, Mar. 2026

IEEE TIMW. Kim, K. Du, H. Lee, N. Kim, J. Rhee*

A Fully Integrated Single-BJT-Based Temperature-to-Digital Converter Achieving ±0.23 °C (3σ) Over 2.0–5.5 V for Duty-Cycled Operation

IEEE Trans. Instrumentation & Measurement, vol. 75, Feb. 2026

2025

IEEE Sensors J.W. Kim, S. Park, J. Yang, J. Jun, S. Kim, J. Rhee*

A Wide Dynamic Range Optical Particulate Matter Sensor with On-chip Machine Learning Calibration

IEEE Sensors Journal, vol. 25, no. 22, Nov. 15, 2025

PwrSoCH. Yoo, S. Oh, D. Kim, C. Kang, J. Won, M. Jeong, H. Lee, Y. Kim, K. Heo, K. Yoon, J. Rhee*

Fast-transient Capacitor-less LDO Using Auxiliary Body-Driven Circuit

Int. Workshop on Power Supply on Chip (PwrSoC), Sep. 2025

IEEE Sensors J.J. Kang, J. Rhee, S. Kim, J. Jun

A 21.6-bit Programmable-Gain Triple-Sampling Incremental ΔΣ ADC With 4 ppm INL for Bridge Transducers

IEEE Sensors Journal, vol. 25, no. 13, pp. 24579–24587, Jul. 1, 2025

IEEE TCAS-IJ. Park, W. Kim, D. Han, H. Lee, S. Kim, J. Rhee*

A 13.2-kSPS Data Rate, 5.1-GΩ Input Impedance Read-Out IC for DC Measurements

IEEE Trans. Circuits & Systems I, vol. 72, no. 7, Jul. 2025

IEEE TPELJ. Yang, H. Lee, J. Cho, K. Lim, HC. Kim, S. Kim, J. Rhee*

A 5.5W-to-276W Integrated Photovoltaic Energy Harvesting System with 99.95% MPPT Efficiency and 98.74% Power Conversion Efficiency

IEEE Trans. Power Electronics, vol. 40, no. 3, Mar. 2025

2023

IEEE Sensors J.M. Kim, S. Han, S. Kim, J. Rhee*

A 105 dB Effective Dynamic Range Self-Capacitance Proximity Sensing System with Consecutive Double-sided Conversion Technique

IEEE Sensors Journal, vol. 23, no. 16, pp. 18325–18337, Aug. 15, 2023

IEEE SensorsJ. Rhee (Invited)

A 17.6-bit 800-SPS Energy-Efficient Read-Out IC with Input Impedance Boosting

IEEE Sensors Conference, Oct. 2023 · Invited Presentation

IEEE Sensors J.J. Park, W. Kim, D. Lee, D. Lee, Y. Hong, S. Kim, J. Rhee*

A 17.6-bit 800-SPS Energy-Efficient Read-Out IC with Input Impedance Boosting

IEEE Sensors Journal, vol. 23, no. 9, pp. 9430–9439, May 1, 2023

ICEICS. Park, W. Kim, S. Kim, J. Rhee*

A 133.3 dB Dynamic Range Pulse Oximeter Front-End With Low-Noise Area-Efficient Offset Cancellation Current DAC

Int. Conf. on Electronics, Information, and Communication (ICEIC), Feb. 2023

ICEICJ. Kang, S. Park, S. Kim, J. Rhee*

56-To-110 dB Gain Programmable Gain Amplifier With Second-Order Band Pass Filter for Ultrasonic Sensor Systems

Int. Conf. on Electronics, Information, and Communication (ICEIC), Feb. 2023

2021

IEEE Sensors J.J. Rhee, H. Kim, H. Yang, S. Kim, H. Lee

Under-Display Optical Proximity Sensor with Silicon Nanowires

IEEE Sensors Journal, vol. 21, no. 18, pp. 20239–20247, Sep. 15, 2021

2020

IEEE Sensors J.J. Rhee, H. Yang, S. Kim

A PM1, PM2.5, and PM10 Airborne Particle Detector with Laser Illumination Stabilized by Optical Feedback

IEEE Sensors Journal, vol. 20, no. 4, pp. 1988–1996, Feb. 15, 2020

IEEE JSSCJ. Rhee, J. Park, S. Kim

A 0.3 lx–1.4 Mlx Monolithic Silicon Nanowire Light-to-Digital Converter with Temperature-Independent Offset Cancellation

IEEE Journal of Solid-State Circuits, vol. 55, no. 2, pp. 378–391, Feb. 2020

IEEE TCAS-IIS. Kim, J. Rhee (equal contribution), S. Kim

A Wide Dynamic Range Multi-Mode Band-Pass Continuous-Time Delta-Sigma Modulator Employing Single-Opamp Resonator with Positive Resistor-Feedback

IEEE Trans. Circuits & Systems II, vol. 67, no. 2, pp. 235–239, Feb. 2020

2019

Electronics Lett.J. Rhee, S. Kim

An 8.4-to-16-bit resolution, 1-to-16 kHz bandwidth ADC with programmable-gain functionality for multi-sensor applications

Electronics Letters, vol. 55, no. 18, pp. 982–984, Sep. 2019

2018

IEEE TCAS-IIJ. S. Cho, J. Rhee, S. Kim, Y. T. Yang, J. H. Jun, H. Lee, S. Kim

A 1.2-V 108.9-dB A-Weighted DR 101.4-dB SNDR Audio ΣΔ ADC Using a Multi-Rate Noise-Shaping Quantizer

IEEE Trans. Circuits & Systems II, vol. 65, no. 10, pp. 1315–1319, Oct. 2018

IEEE ISSCCJ. Jun, J. Rhee, MS. Kim, J. Kang, S. Kim

A 21.8-bit Sub-100 µHz 1/f Corner 2.4 µV Offset Programmable-Gain Read-Out IC for Bridge Measurement Systems

IEEE Int. Solid-State Circuits Conference (ISSCC), Feb. 2018

2017

IEEE Sensors J.J. Jun, J. Rhee, S. Kim, S. Kim

An SC Interface with Programmable-Gain Embedded ΔΣ ADC for Monolithic 3-Axis 3-D Stacked Capacitive MEMS Accelerometer

IEEE Sensors Journal, vol. 17, no. 17, pp. 5558–5568, Sep. 2017

2016

IEEE TCAS-IIH. Lee, D. Shim, J. Rhee, M. Kim, S. Kim

A Sub-1.0V On-Chip CMOS Thermometer with a Folded Temperature Sensor for Low-Power Mobile DRAM

IEEE Trans. Circuits & Systems II, vol. 63, no. 6, pp. 553–557, Jun. 2016

IEEE ISLPEDJ. Jun, J. Rhee, S. Kim

A 386-µW, 15.2-bit Programmable-Gain Embedded Delta-Sigma ADC for Sensor Applications

IEEE Int. Symp. on Low Power Electronics and Design (ISLPED), Aug. 2016

ICEICJ. Rhee, S. Kim

A low power, small-area and linearity-compensated CMOS temperature sensor

Int. Conf. on Electronics, Information, and Communication (ICEIC), Jan. 2016

2015

ITC-CSCCJ. S. Cho, H. Lee, J. Rhee, S. Kim

Design of a Stereo Audio Sigma-Delta ADC with 92.4 dB SNR and −88.3 dB THD+N

30th Int. Technical Conf. on Circuits/Systems, Computers and Communications (ITC-CSCC), pp. 611–612, Jun. 2015

2013

IEEE JSSCD. Shim, H. Jeong, H. Lee, J. Rhee, DK. Jeong, S. Kim

A Process-Variation-Tolerant On-Chip CMOS Thermometer for Auto Temperature Compensated Self-Refresh of Low-Power Mobile DRAM

IEEE Journal of Solid-State Circuits, vol. 48, no. 10, pp. 2550–2557, Oct. 2013

2012

IEEE SoCCS. Kim, SI. Na, TH. Kim, H. Lee, S. Kim, J. Rhee, S. Kim

Neural Recording System with Low-Noise Analog Front-End and Comparator-Based Cyclic ADC

IEEE Int. SoC Conference (SoCC), pp. 110–114, Sep. 2012

03 Principal Investigator

Professor

Jooyeol Rhee 이주열

Assistant Professor

Department of System Semiconductor, Gachon University

Education

2012.03 – 2019.02 Ph.D., Electrical Engineering and Computer ScienceSeoul National University (SNU), Seoul, Korea
2010.09 – 2011.11 M.Eng., Electrical EngineeringUniversity of Toronto, ON, Canada
2005.09 – 2010.06 B.S., Electrical and Computer EngineeringUniversity of Toronto, ON, Canada

Professional Experience

2022.09 – Present Assistant ProfessorDepartment of System Semiconductor, Gachon University, Seongnam, Korea
2019.10 – 2022.08 Staff EngineerSamsung Electronics, Hwaseong, Korea
2019.03 – 2019.09 Postdoctoral FellowSeoul National University (SNU), Seoul, Korea

Research Interests

Precision Analog Circuits
High-precision Analog-to-Digital Converters (ADCs)
Power Management Integrated Circuits (PMICs)
Digital-Assisted Analog / Mixed-Signal Circuits
Digital Calibration and Correction Techniques

04 People

Members

The AXIS Design Laboratory brings together graduate researchers working across precision analog design, data converters, power management, and in-sensor computing.

Graduate Researchers