Youngcheol Chae

Bio: Youngcheol Chae is an academic researcher from Yonsei University. The author has contributed to research in topics: CMOS & Image sensor. The author has an hindex of 24, co-authored 124 publications receiving 2991 citations. Previous affiliations of Youngcheol Chae include Samsung & Delft University of Technology.

Low Voltage, Low Power, Inverter-Based Switched-Capacitor Delta-Sigma Modulator

Abstract: An operational transconductance amplifier (OTA) is a major building block and consumes most of the power in switched-capacitor (SC) circuits, but it is difficult to design low-voltage OTAs in scaled CMOS technologies. Instead of using an OTA, this paper proposes an inverter-based SC circuit and its application to low-voltage, low-power delta-sigma (DeltaSigma) modulators. Detailed analysis and design optimizations are also provided. Three inverter-based DeltaSigma modulators are implemented for an implantable pacemaker, a CMOS image sensor, and an audio codec. The modulator-I for an implantable pacemaker achieves 65-dB peak-SNDR for 120-Hz bandwidth consuming 0.73 muW with 1.5 V supply. The modulator-II for a CMOS image sensor implemented with 320-channel parallel ADC architecture achieves 63-dB peak-SNDR for 8-kHz bandwidth consuming 5.6 muW for each channel with 1.2-V supply. The modulator-III for an audio codec achieves 81-dB peak-SNDR with 20-kHz bandwidth consuming 36 muW with 0.7-V supply. The prototype DeltaSigma modulators achieved high power efficiency maintaining sufficient performances for practical applications.

Graphene-Based Three-Dimensional Capacitive Touch Sensor for Wearable Electronics

Abstract: The development of input device technology in a conformal and stretchable format is important for the advancement of various wearable electronics. Herein, we report a capacitive touch sensor with good sensing capabilities in both contact and noncontact modes, enabled by the use of graphene and a thin device geometry. This device can be integrated with highly deformable areas of the human body, such as the forearms and palms. This touch sensor detects multiple touch signals in acute recordings and recognizes the distance and shape of the approaching objects before direct contact is made. This technology offers a convenient and immersive human–machine interface and additional potential utility as a multifunctional sensor for emerging wearable electronics and robotics.

A CMOS Temperature Sensor With a Voltage-Calibrated Inaccuracy of $\pm$ 0.15 $ ^{\circ}$ C (3 $\sigma$ ) From $-$ 55 $^{\circ}$ C to 125 $^{\circ}$ C

Abstract: This paper describes the design of a low power, energy-efficient CMOS smart temperature sensor intended for RFID temperature sensing. The BJT-based sensor employs an energy- efficient 2nd-order zoom ADC, which combines a coarse 5-bit SAR conversion with a fine 10-bit ΔΣ conversion. Moreover, a new integration scheme is proposed that halves the conversion time, while requiring no extra supply current. To meet the stringent cost constraints on RFID tags, a fast voltage calibration technique is used, which can be carried out in only 200 msec. After batch calibration and an individual room-temperature calibration, the sensor achieves an inaccuracy of ±0.15°C (3σ) from -55°C to 125°C . Over the same range, devices from a second lot achieved an inaccuracy of ±0.25°C (3σ) in both ceramic and plastic packages. The sensor occupies 0.08 mm2 in a 0.16 μm CMOS process, draws 3.4 μA from a 1.5 V to 2 V supply, and achieves a resolution of 20 mK in a conversion time of 5.3 msec. This corresponds to a minimum energy dissipation of 27 nJ per conversion.

A 2.1 M Pixels, 120 Frame/s CMOS Image Sensor With Column-Parallel $\Delta \Sigma$ ADC Architecture

Abstract: This paper presents a 2.1 M pixel, 120 frame/s CMOS image sensor with column-parallel delta-sigma (ΔΣ) ADC architecture. The use of a second-order ΔΣ ADC improves the conversion speed while reducing the random noise (RN) level as well. The ΔΣ ADC employing an inverter-based ΔΣ modulator and a compact decimation filter is accommodated within a fine pixel pitch of 2.25-μm and improves energy efficiency while providing a high frame-rate of 120 frame/s. A prototype image sensor has been fabricated with a 0.13-μm CMOS process. Measurement results show a RN of 2.4 erms- and a dynamic range of 73 dB. The power consumption of the prototype image sensor is only 180 mW. This work achieves the energy efficiency of 1.7 e-·nJ.

Recent progress of molecular organic electroluminescent materials and devices

Abstract: Electroluminescent devices based on organic materials are of considerable interest owing to their attractive characteristics and potential applications to flat panel displays. After a brief overview of the device construction and operating principles, a review is presented on recent progress in organic electroluminescent materials and devices. Small molecular materials are described with emphasis on their material issues pertaining to charge transport, color, and luminance efficiencies. The chemical nature of electrode/organic interfaces and its impact on device performance are then discussed. Particular attention is paid to recent advances in interface engineering that is of paramount importance to modify the chemical and electronic structure of the interface. The topics in this report also include recent development on the enhancement of electron transport capability in organic materials by doping and the increase in luminance efficiency by utilizing electrophosphorescent materials. Of particular interest for the subject of this review are device reliability and its relationship with material characteristics and interface structures. Important issues relating to display fabrication and the status of display development are briefly addressed as well.

Design Of Analog Cmos Integrated Circuits

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