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Seokhyeon Jeong

Bio: Seokhyeon Jeong is an academic researcher from University of Michigan. The author has contributed to research in topics: CMOS & Comparator. The author has an hindex of 17, co-authored 42 publications receiving 902 citations.

Papers
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Journal ArticleDOI
TL;DR: A new sensing element is introduced that outputs only 75 mV to save both power and area in battery-operated, ultra-low power microsystems and is integrated into a wireless sensor node to demonstrate its operation at a system level.
Abstract: We propose a fully-integrated temperature sensor for battery-operated, ultra-low power microsystems. Sensor operation is based on temperature independent/dependent current sources that are used with oscillators and counters to generate a digital temperature code. A conventional approach to generate these currents is to drop a temperature sensitive voltage across a resistor. Since a large resistance is required to achieve nWs of power consumption with typical voltage levels (100 s of mV to 1 V), we introduce a new sensing element that outputs only 75 mV to save both power and area. The sensor is implemented in 0.18 μm CMOS and occupies 0.09 mm 2 while consuming 71 nW. After 2-point calibration, an inaccuracy of + 1.5°C/-1.4°C is achieved across 0 °C to 100 °C. With a conversion time of 30 ms, 0.3 °C (rms) resolution is achieved. The sensor does not require any external references and consumes 2.2 nJ per conversion. The sensor is integrated into a wireless sensor node to demonstrate its operation at a system level.

157 citations

Proceedings ArticleDOI
09 Jun 2014
TL;DR: This paper explores the IoT application space and identifies two common challenges that exist across this space: ultra-low power operation and system design using modular, composable components.
Abstract: The Internet of Things (IoT) is a rapidly emerging application space, poised to become the largest electronics market for the semiconductor industry. IoT devices are focused on sensing and actuating of our physical environment and have a nearly unlimited breadth of uses. In this paper, we explore the IoT application space and then identify two common challenges that exist across this space: ultra-low power operation and system design using modular, composable components. We survey recent low power techniques and discuss a low power bus that enables modular design. Finally, we conclude with three example ultra-low power, millimeter-scale IoT systems.

149 citations

Proceedings ArticleDOI
19 Mar 2015
TL;DR: A fully digital capacitance-to-digital converters (CDC) is presented that is based on the observation that when a ring oscillator is powered from a charged capacitance, the number of RO cycles required to discharge the capacitance to a fixed voltage is naturally linear with the capacitor value.
Abstract: Capacitance sensors are widely used to measure various physical quantities, including position, pressure, and concentration of certain chemicals [1-6]. Integrating capacitive sensors into a small wireless sensor system is challenging due to their large power consumption relative to the total system power/energy budget, which can be as low as a few nW [4]. Typical capacitance-to-digital converters (CDCs) use charge sharing or charge transfer between capacitors to convert the sampled capacitance to voltage, which is then measured with an ADC [1-6]. This approach requires complex analog circuits, such as amplifiers and ADCs, increasing design complexity and often increasing power consumption. Moreover, the initial capacitance to voltage conversion essentially limits the input capacitance range because of output voltage saturation. This paper presents a fully digital CDC that is based on the observation that when a ring oscillator (RO) is powered from a charged capacitance, the number of RO cycles required to discharge the capacitance to a fixed voltage is naturally linear with the capacitance value. This observation enables a simple, fully digital conversion scheme that is inherently linear. As a result, the proposed CDC performs conversion across a very wide capacitance range from 0.7pF to over 10nF with < 0.06% linearity error. The CDC senses 11.3pF input capacitance with 35.1 pJ conversion energy and 141fJ/c-s FoM.

71 citations

Proceedings ArticleDOI
10 Jun 2014
TL;DR: A 2×4×4mm3 imaging system complete with optics, wireless communication, battery, power management, solar harvesting, processor and memory, and the system features a 160×160 resolution CMOS image sensor with 304nW continuous in-pixel motion detection mode is presented.
Abstract: We present a 2×4×4mm 3 imaging system complete with optics, wireless communication, battery, power management, solar harvesting, processor and memory. The system features a 160×160 resolution CMOS image sensor with 304nW continuous in-pixel motion detection mode. System components are fabricated in five different IC layers and die-stacked for minimal form factor. Photovoltaic (PV) cells face the opposite direction of the imager for optimal illumination and generate 456nW at 10klux to enable energy autonomous system operation.

64 citations

Journal ArticleDOI
TL;DR: A detailed analysis of the EPC in the phase domain shows improved energy efficiency over conventional comparators even without energy scaling, and wider resolution tuning capability with small load capacitance and area.
Abstract: This paper presents a new energy-efficient ring oscillator collapse-based comparator, named edge-pursuit comparator (EPC). This comparator automatically adjusts the performance by changing the comparison energy according to its input difference without any control, eliminating unnecessary energy spent on coarse comparisons. Furthermore, a detailed analysis of the EPC in the phase domain shows improved energy efficiency over conventional comparators even without energy scaling, and wider resolution tuning capability with small load capacitance and area. The EPC is used in a successive-approximation-register analog-to-digital converter (SAR ADC) design, which supplements a 10 b differential coarse capacitive digital-to-analog converter (CDAC) with a 5 b common-mode CDAC. This offers an additional 5 b of resolution with common mode to differential gain tuning that improves linearity by reducing the effect of switch parasitic capacitance. A test chip fabricated in 40 nm CMOS shows 74.12 dB signal-to-noise and distortion ratio and 173.4 dB Schreier Figure-of-Merit. With the full ADC consuming 1.17 $\mu \text{W}$ , the comparator consumes 104 nW, which is only 8.9% of the full ADC power, proving the comparator’s energy efficiency.

60 citations


Cited by
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Journal ArticleDOI
TL;DR: This review provides a summ ary of radio frequency (RF) power harvesting technologies in order to serve as a guide for the design of RF energy harvesting units.
Abstract: Wireless power transmission was conceptualized nearly a century ago. Certain achievements made to date have made power harvesting a reality, capable of providing alternative sources of energy. This review provides a summ ary of radio frequency (RF) power harvesting technologies in order to serve as a guide for the design of RF energy harvesting units. Since energy harvesting circuits are designed to operate with relatively small voltages and currents, they rely on state-of-the-art electrical technology for obtaining high efficiency. Thus, comprehensive analysis and discussions of various designs and their tradeoffs are included. Finally, recent applications of RF power harvesting are outlined.

185 citations

Journal ArticleDOI
TL;DR: Flexible IoT hierarchical architecture model for smart cities needs a flexible layered architecture where the things, the people and the cloud services are combined to facilitate an application task.

163 citations

Journal ArticleDOI
TL;DR: A critical review of the potential of an IoE-based BEMS for enhancing the performance of future generation building energy utilization and provides several suggestions for the research and development of the advanced optimized controller and IoE of future BEMSs.
Abstract: A building energy management system (BEMS) is a sophisticated method used for monitoring and controlling a building’s energy requirements A number of potential studies were conducted in nearly or net zero energy buildings (nZEBs) for the optimization of building energy consumption through efficient and sustainable ways Moreover, policy makers are approving measures to improve building energy efficiency in order to foster sustainable energy usages However, the intelligence of existing BEMSs or nZEBs is inadequate, because of the static set points for heating, cooling, and lighting, the complexity of large amounts of BEMS data, data loss, and network problems To solve these issues, a BEMS or nZEB solution based on the Internet of energy (IoE) provides disruptive opportunities for revolutionizing sustainable building energy management This paper presents a critical review of the potential of an IoE-based BEMS for enhancing the performance of future generation building energy utilization The detailed studies of the IoE architecture, typical nZEB configuration, different generations of nZEB, and smart building energy systems for future BEMS are investigated The operations, advantages, and limitations of the existing BEMSs or nZEBs are illustrated A comprehensive review of the different types of IoE-based BEMS technologies, such as energy routers, storage systems and materials, renewable sources, and plug-and-play interfaces, is then presented The rigorous review indicates that existing BEMSs require advanced controllers integrated with IoE-based technologies for sustainable building energy usage The main objective of this review is to highlight several issues and challenges of the conventional controllers and IoE applications of BEMSs or nZEBs Accordingly, the review provides several suggestions for the research and development of the advanced optimized controller and IoE of future BEMSs All the highlighted insights and recommendations of this review will hopefully lead to increasing efforts toward the development of the future BEMS applications

162 citations

Journal ArticleDOI
TL;DR: A fully integrated energy harvester that maintains >35% end-to-end efficiency when harvesting from a 0.84 mm 2 solar cell in low light condition of 260 lux, converting 7 nW input power from 250 mV to 4 V is presented.
Abstract: This paper presents a fully integrated energy harvester that maintains >35% end-to-end efficiency when harvesting from a 0.84 mm 2 solar cell in low light condition of 260 lux, converting 7 nW input power from 250 mV to 4 V. Newly proposed self-oscillating switched-capacitor (SC) DC-DC voltage doublers are cascaded to form a complete harvester, with configurable overall conversion ratio from 9× to 23×. In each voltage doubler, the oscillator is completely internalized within the SC network, eliminating clock generation and level shifting power overheads. A single doubler has >70% measured efficiency across 1 nA to 0.35 mA output current ( >10 5 range) with low idle power consumption of 170 pW. In the harvester, each doubler has independent frequency modulation to maintain its optimum conversion efficiency, enabling optimization of harvester overall conversion efficiency. A leakage-based delay element provides energy-efficient frequency control over a wide range, enabling low idle power consumption and a wide load range with optimum conversion efficiency. The harvester delivers 5 nW-5 μW output power with >40% efficiency and has an idle power consumption 3 nW, in test chip fabricated in 0.18 μm CMOS technology.

148 citations

Journal ArticleDOI
TL;DR: In this paper, a spiral shaped microelectromechanical system (MEMS) energy harvester was designed to harvest ambient vibrations at a low frequency exhibiting remanent polarization of 36.2
Abstract: We demonstrate a microscale vibration energy harvester exhibiting an ultra-low resonance frequency and high power density. A spiral shaped microelectromechanical system (MEMS) energy harvester was designed to harvest ambient vibrations at a low frequency ( $\mu \text{m}$ -thickness exhibiting remanent polarization of 36.2 $\mu \text{C}$ /cm2 and longitudinal piezoelectric constant of 155 pm/V was synthesized to achieve high efficiency mechanical to electrical conversion. The experimental results demonstrate an ultra-low natural frequency of 48 Hz for MEMS harvester. This is one of the lowest resonance frequency reported for the piezoelectric MEMS energy harvester. Further, the position of the natural frequency was controlled by modulating the number of spiral turns and weight of the proof mass. The vibration mode shape and stress distribution were validated through a finite element analysis. The maximum output power of 23.3 nW was obtained from the five turns spiral MEMS energy harvester excited at 0.25 g acceleration and 68Hz. The normalized area and the volumetric energy density were measured to be $5.04\times 10^{-4}~ \mu \text{W}$ /mm $^{2}~\cdot ~\text{g}^{2}~\cdot$ Hz and $4.92\times 10^{-2} ~ \mu \text{W}$ /mm $^{3}~\cdot ~\text{g}^{2}~\cdot$ Hz, respectively. [2017-0018]

125 citations