Energy-Efficient Capacitance-to-Digital Converters for Low-Energy Sensor Nodes

Handle URI:
http://hdl.handle.net/10754/582481
Title:
Energy-Efficient Capacitance-to-Digital Converters for Low-Energy Sensor Nodes
Authors:
Omran, Hesham ( 0000-0002-0117-7364 )
Abstract:
Energy efficiency is a key requirement for wireless sensor nodes, biomedical implants, and wearable devices. The energy consumption of the sensor node needs to be minimized to avoid battery replacement, or even better, to enable the device to survive on energy harvested from the ambient. Capacitive sensors do not consume static power; thus, they are attractive from an energy efficiency perspective. In addition, they can be employed in a wide range of sensing applications. However, the sensor readout circuit–i.e., the capacitance-to-digital converter (CDC)–can be the dominant source of energy consumption in the system. Thus, the development of energy-efficient CDCs is crucial to minimizing the energy consumption of capacitive sensor nodes. In the first part of this dissertation, we propose several energy-efficient CDC architectures for low-energy sensor nodes. First, we propose a digitally-controlled coarsefine multislope CDC that employs both current and frequency scaling to achieve significant improvement in energy efficiency. Second, we analyze the limitations of successive approximation (SAR) CDC, and we address these limitations by proposing a robust parasitic-insensitive opamp-based SAR CDC. Third, we propose an inverter-based SAR CDC that achieves an energy efficiency figure-of-merit (FoM) of 31fJ/Step, which is the best energy efficiency FoM reported to date. Fourth, we propose a differential SAR CDC with quasi-dynamic operation to maintain excellent energy efficiency for a scalable sample rate. In the second part of this dissertation, we study the matching properties of small integrated capacitors, which are an integral component of energy-efficient CDCs. Despite conventional wisdom, we experimentally illustrate that the mismatch of small capacitors can be directly measured, and we report mismatch measurements for subfemtofarad integrated capacitors. We also correct the common misconception that lateral capacitors match better than vertical capacitors, and we identify the conditions that make one implementation preferable. In the third and last part of this dissertation, we investigate the potential of novel metal-organic framework (MOF) thin films in capacitive gas sensing. We provide sensitivity-based optimization and simple fabrication flow for capacitive interdigitated electrodes. We use a custom flexible gas sensor test setup that is designed and built in-house to characterize MOF-based capacitive gas sensors.
Advisors:
Salama, Khaled N. ( 0000-0001-7742-1282 )
Committee Member:
Kosel, Jürgen ( 0000-0002-8998-8275 ) ; Eddaoudi, Mohamed ( 0000-0003-1916-9837 ) ; Sylvester, Dennis; Al-Attar, Talal
KAUST Department:
Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division; Electrical Engineering Program
Program:
Electrical Engineering
Issue Date:
Nov-2015
Type:
Dissertation
Appears in Collections:
Dissertations; Electrical Engineering Program; Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division

Full metadata record

DC FieldValue Language
dc.contributor.advisorSalama, Khaled N.en
dc.contributor.authorOmran, Heshamen
dc.date.accessioned2015-11-22T08:15:17Zen
dc.date.available2015-11-22T08:15:17Zen
dc.date.issued2015-11en
dc.identifier.urihttp://hdl.handle.net/10754/582481en
dc.description.abstractEnergy efficiency is a key requirement for wireless sensor nodes, biomedical implants, and wearable devices. The energy consumption of the sensor node needs to be minimized to avoid battery replacement, or even better, to enable the device to survive on energy harvested from the ambient. Capacitive sensors do not consume static power; thus, they are attractive from an energy efficiency perspective. In addition, they can be employed in a wide range of sensing applications. However, the sensor readout circuit–i.e., the capacitance-to-digital converter (CDC)–can be the dominant source of energy consumption in the system. Thus, the development of energy-efficient CDCs is crucial to minimizing the energy consumption of capacitive sensor nodes. In the first part of this dissertation, we propose several energy-efficient CDC architectures for low-energy sensor nodes. First, we propose a digitally-controlled coarsefine multislope CDC that employs both current and frequency scaling to achieve significant improvement in energy efficiency. Second, we analyze the limitations of successive approximation (SAR) CDC, and we address these limitations by proposing a robust parasitic-insensitive opamp-based SAR CDC. Third, we propose an inverter-based SAR CDC that achieves an energy efficiency figure-of-merit (FoM) of 31fJ/Step, which is the best energy efficiency FoM reported to date. Fourth, we propose a differential SAR CDC with quasi-dynamic operation to maintain excellent energy efficiency for a scalable sample rate. In the second part of this dissertation, we study the matching properties of small integrated capacitors, which are an integral component of energy-efficient CDCs. Despite conventional wisdom, we experimentally illustrate that the mismatch of small capacitors can be directly measured, and we report mismatch measurements for subfemtofarad integrated capacitors. We also correct the common misconception that lateral capacitors match better than vertical capacitors, and we identify the conditions that make one implementation preferable. In the third and last part of this dissertation, we investigate the potential of novel metal-organic framework (MOF) thin films in capacitive gas sensing. We provide sensitivity-based optimization and simple fabrication flow for capacitive interdigitated electrodes. We use a custom flexible gas sensor test setup that is designed and built in-house to characterize MOF-based capacitive gas sensors.en
dc.language.isoenen
dc.subjectcapacitance-to-digital converter (CDC)en
dc.subjectcapacitive sensor readout circuiten
dc.subjectenergy efficient circuitsen
dc.subjectsuccessive approximation register (SAR)en
dc.subjectcapacitor mismatchen
dc.subjectgas sensoren
dc.titleEnergy-Efficient Capacitance-to-Digital Converters for Low-Energy Sensor Nodesen
dc.typeDissertationen
dc.contributor.departmentComputer, Electrical and Mathematical Sciences and Engineering (CEMSE) Divisionen
dc.contributor.departmentElectrical Engineering Programen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberKosel, Jürgenen
dc.contributor.committeememberEddaoudi, Mohameden
dc.contributor.committeememberSylvester, Dennisen
dc.contributor.committeememberAl-Attar, Talalen
thesis.degree.disciplineElectrical Engineeringen
thesis.degree.nameDoctor of Philosophyen
dc.person.id115166en
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