54 research outputs found
Novel Current-Mode Sensor Interfacing and Radio Blocks for Cell Culture Monitoring
Since 2004 Imperial College has been developing the world’s first application-specific
instrumentation aiming at the on-line, in-situ, physiochemical monitoring of adult stem
cell cultures. That effort is internationally known as the ‘Intelligent Stem Cell Culture
Systems’ (ISCCS) project. The ISCCS platform is formed by the functional integration
of biosensors, interfacing electronics and bioreactors. Contrary to the PCB-level
ISCCS platform the work presented in this thesis relates to the realization of a miniaturized
cell culture monitoring platform. Specifically, this thesis details the synthesis and
fabrication of pivotal VLSI circuit blocks suitable for the construction of a miniaturized
microelectronic cell monitoring platform. The thesis is composed of two main parts.
The first part details the design and operation of a two-stage current-input currentoutput
topology suitable for three-electrode amperometric sensor measurements. The
first stage is a CMOS-dual rail-class AB-current conveyor providing a low impedancevirtual
ground node for a current input. The second stage is a novel hyperbolic-sinebased
externally-linear internally-non-linear current amplification stage. This stage
bases its operation upon the compressive sinh−1 conversion of the interfaced current
to an intermediate auxiliary voltage and the subsequent sinh expansion of the same
voltage. The proposed novel topology has been simulated for current-gain values ranging
from 10 to 1000 using the parameters of the commercially available 0.8μm AMS
CMOS process. Measured results from a chip fabricated in the same technology are also
reported. The proposed interfacing/amplification architecture consumes 0.88-95μW. The second part describes the design and practical evaluation of a 13.56MHz frequency
shift keying (FSK) short-range (5cm) telemetry link suitable for the monitoring of incubated
cultures. Prior to the design of the full FSK radio system, a pair of 13.56MHz
antennae are characterized experimentally. The experimental S-parameter-value determination
of the 13.56MHz wireless link is incorporated into the Cadence Design
Framework allowing a high fidelity simulation of the reported FSK radio. The transmitter
of the proposed system is a novel multi-tapped seven-stage ring-oscillator-based
VCO whereas the core of the receiver is an appropriately modified phase locked loop
(PLL). Simulated and measured results from a 0.8μm CMOS technology chip are reported
Low-Power and Programmable Analog Circuitry for Wireless Sensors
Embedding networks of secure, wirelessly-connected sensors and actuators will help us to conscientiously manage our local and extended environments. One major challenge for this vision is to create networks of wireless sensor devices that provide maximal knowledge of their environment while using only the energy that is available within that environment. In this work, it is argued that the energy constraints in wireless sensor design are best addressed by incorporating analog signal processors. The low power-consumption of an analog signal processor allows persistent monitoring of multiple sensors while the device\u27s analog-to-digital converter, microcontroller, and transceiver are all in sleep mode. This dissertation describes the development of analog signal processing integrated circuits for wireless sensor networks. Specific technology problems that are addressed include reconfigurable processing architectures for low-power sensing applications, as well as the development of reprogrammable biasing for analog circuits
Low-Power and Programmable Analog Circuitry for Wireless Sensors
Embedding networks of secure, wirelessly-connected sensors and actuators will help us to conscientiously manage our local and extended environments. One major challenge for this vision is to create networks of wireless sensor devices that provide maximal knowledge of their environment while using only the energy that is available within that environment. In this work, it is argued that the energy constraints in wireless sensor design are best addressed by incorporating analog signal processors. The low power-consumption of an analog signal processor allows persistent monitoring of multiple sensors while the device\u27s analog-to-digital converter, microcontroller, and transceiver are all in sleep mode. This dissertation describes the development of analog signal processing integrated circuits for wireless sensor networks. Specific technology problems that are addressed include reconfigurable processing architectures for low-power sensing applications, as well as the development of reprogrammable biasing for analog circuits
System-level design and RF front-end implementation for a 3-10ghz multiband-ofdm ultrawideband receiver and built-in testing techniques for analog and rf integrated circuits
This work consists of two main parts: a) Design of a 3-10GHz UltraWideBand
(UWB) Receiver and b) Built-In Testing Techniques (BIT) for Analog and RF circuits.
The MultiBand OFDM (MB-OFDM) proposal for UWB communications has
received significant attention for the implementation of very high data rate (up to
480Mb/s) wireless devices. A wideband LNA with a tunable notch filter, a downconversion
quadrature mixer, and the overall radio system-level design are proposed for
an 11-band 3.4-10.3GHz direct conversion receiver for MB-OFDM UWB implemented
in a 0.25mm BiCMOS process. The packaged IC includes an RF front-end with
interference rejection at 5.25GHz, a frequency synthesizer generating 11 carrier tones in
quadrature with fast hopping, and a linear phase baseband section with 42dB of gain
programmability. The receiver IC mounted on a FR-4 substrate provides a maximum
gain of 67-78dB and NF of 5-10dB across all bands while consuming 114mA from a
2.5V supply.
Two BIT techniques for analog and RF circuits are developed. The goal is to reduce
the test cost by reducing the use of analog instrumentation. An integrated frequency response characterization system with a digital interface is proposed to test the
magnitude and phase responses at different nodes of an analog circuit. A complete
prototype in CMOS 0.35mm technology employs only 0.3mm2 of area. Its operation is
demonstrated by performing frequency response measurements in a range of 1 to
130MHz on 2 analog filters integrated on the same chip. A very compact CMOS RF
RMS Detector and a methodology for its use in the built-in measurement of the gain and
1dB compression point of RF circuits are proposed to address the problem of on-chip
testing at RF frequencies. The proposed device generates a DC voltage proportional to
the RMS voltage amplitude of an RF signal. A design in CMOS 0.35mm technology
presents and input capacitance <15fF and occupies and area of 0.03mm2. The application
of these two techniques in combination with a loop-back test architecture significantly
enhances the testability of a wireless transceiver system
Integrated Circuits for Programming Flash Memories in Portable Applications
Smart devices such as smart grids, smart home devices, etc. are infrastructure systems that connect the world around us more than before. These devices can communicate with each other and help us manage our environment. This concept is called the Internet of Things (IoT). Not many smart nodes exist that are both low-power and programmable. Floating-gate (FG) transistors could be used to create adaptive sensor nodes by providing programmable bias currents. FG transistors are mostly used in digital applications like Flash memories. However, FG transistors can be used in analog applications, too. Unfortunately, due to the expensive infrastructure required for programming these transistors, they have not been economical to be used in portable applications. In this work, we present low-power approaches to programming FG transistors which make them a good candidate to be employed in future wireless sensor nodes and portable systems. First, we focus on the design of low-power circuits which can be used in programming the FG transistors such as high-voltage charge pumps, low-drop-out regulators, and voltage reference cells. Then, to achieve the goal of reducing the power consumption in programmable sensor nodes and reducing the programming infrastructure, we present a method to program FG transistors using negative voltages. We also present charge-pump structures to generate the necessary negative voltages for programming in this new configuration
A high-frequency quad-modulus prescaler for fractional-N frequency synthesizer
Master'sMASTER OF ENGINEERIN
Low-Power Reconfigurable Sensing Circuitry for the Internet-of-Things Paradigm
With ubiquitous wireless communication via Wi-Fi and nascent 5th Generation mobile communications, more devices -- both smart and traditionally dumb -- will be interconnected than ever before. This burgeoning trend is referred to as the Internet-of-Things. These new sensing opportunities place a larger burden on the underlying circuitry that must operate on finite battery power and/or within energy-constrained environments. New developments of low-power reconfigurable analog sensing platforms like field-programmable analog arrays (FPAAs) present an attractive sensing solution by processing data in the analog domain while staying flexible in design. This work addresses some of the contemporary challenges of low-power wireless sensing via traditional application-specific sensing and with FPAAs. A large emphasis is placed on furthering the development of FPAAs by making them more accessible to designers without a strong integrated-circuit background -- much like FPGAs have done for digital designers
Impedance matching and DC-DC converter designs for tunable radio frequency based mobile telecommunication systems
Tunability and adaptability for radio frequency (RF) front-ends are highly desirable because
they not only enhance functionality and performance but also reduce the circuit size and cost.
This thesis presents a number of novel design strategies in DC-DC converters, impedance
networks and adaptive algorithms for tunable and adaptable RF based mobile
telecommunication systems. Specifically, the studies are divided into three major directions:
(a) high voltage switch controller based DC-DC converters for RF switch actuation; (b)
impedance network designs for impedance transformation of RF switches; and (c) adaptive
algorithms for determining the required impedance states at the RF switches.
In the first stage, two-phase step-up switched-capacitor (SC) DC-DC converters are
explored. The SC converter has a simple control method and a reduced physical volume. The
research investigations started with the linear and the non-linear voltage gain topologies. The
non-linear voltage gain topology provides a higher voltage gain in a smaller number of
stages compared to the linear voltage gain topology. Amongst the non-linear voltage gain
topologies, a Fibonacci SC converter has been identified as having lower losses and a higher
conversion ratio compared to other topologies. However, the implementation of a high
voltage (HV) gain Fibonacci SC converter is complex due to the requirement of widely
different gate voltages for the transistors in the Fibonacci converter. Gate driving strategies
have been proposed that only require a few auxiliary transistors in order to provide the
required boosted voltages for switching the transistors on and off. This technique reduces the
design complexity and increases the reliability of the HV Fibonacci SC converter.
For the linear voltage gain topology, a high performance complementary-metaloxide-
semiconductor (CMOS) based SC DC-DC converter has been proposed in this work.
The HV SC DC-DC converter has been designed in low voltage (LV) transistors technology
in order to achieve higher voltage gain. Adaptive biasing circuits have been proposed to
eliminate the leakage current, hence avoiding latch-up which normally occurs with low
voltage transistors when they are used in a high voltage design. Thus, the SC DC-DC
converter achieves more than 25% higher boosted voltage compared to converters that use
HV transistors. The proposed design provides a 40% power reduction through the charge
recycling circuit that reduces the effect of non-ideality in integrated HV capacitors.
Moreover, the SC DC-DC converter achieves a 45% smaller area than the conventional
converter through optimising the design parameters. In the second stage, the impedance network designs for transforming the impedance
of RF switches to the maximum achievable impedance tuning region are investigated. The
maximum achievable tuning region is bounded by the fundamental properties of the selected
impedance network topology and by the tunable values of the RF switches that are variable
over a limited range. A novel design technique has been proposed in order to achieve the
maximum impedance tuning region, through identifying the optimum electrical distance
between the RF switches at the impedance network. By varying the electrical distance
between the RF switches, high impedance tuning regions are achieved across multi
frequency standards. This technique reduces the cost and the insertion loss of an impedance
network as the required number of RF switches is reduced. The prototype demonstrates high
impedance coverages at LTE (700MHz), GSM (900MHz) and GPS (1575MHz).
Integration of a tunable impedance network with an antenna for frequency-agility at
the RF front-end has also been discussed in this work. The integrated system enlarges the
bandwidth of a patch antenna by four times the original bandwidth and also improves the
antenna return loss. The prototype achieves frequency-agility from 700MHz to 3GHz. This
work demonstrates that a single transceiver with multi frequency standards can be realised
by using a tunable impedance network.
In the final stage, improvement to an adaptive algorithm for determining the
impedance states at the RF switches has been proposed. The work has resulted in one more
novel design techniques which reduce the search time in the algorithm, thus minimising the
risk of data loss during the impedance tuning process. The approach reduces the search time
by more than an order of magnitude by exploiting the relationships among the mass spring’s
coefficient values derived from the impedance network parameters, thereby significantly
reducing the convergence time of the algorithm. The algorithm with the proposed technique
converges in less than half of the computational time compared to the conventional
approach, hence significantly improving the search time of the algorithm.
The design strategies proposed in this work contribute towards the realisation of
tunable and adaptable RF based mobile telecommunication systems
Design of Power Management Integrated Circuits and High-Performance ADCs
A battery-powered system has widely expanded its applications to implantable medical devices
(IMDs) and portable electronic devices. Since portable devices or IMDs operate in the
energy-constrained environment, their low-power operations in combination with efficiently sourcing
energy to them are key problems to extend device life. This research proposes novel circuit
techniques for two essential functions of a power receiving unit (PRU) in the energy-constrained
environment, which are power management and signal processing.
The first part of this dissertation discusses power management integrated circuits for a PRU.
From a power management perspective, the most critical two circuit blocks are a front-end rectifier
and a battery charger. The front-end CMOS active rectifier converts transmitted AC power into
DC power. High power conversion efficiency (PCE) is required to reduce power loss during the
power transfer, and high voltage conversion ratio (VCR) is required for the rectifier to enable low-voltage
operations. The proposed 13.56-MHz CMOS active rectifier presents low-power circuit
techniques for comparators and controllers to reduce increasing power loss of an active diode with
offset/delay calibration. It is implemented with 5-V devices of a 0.35 µm CMOS process to support
high voltage. A peak PCE of 89.0%, a peak VCR of 90.1%, and a maximum output power of 126.7
mW are measured for 200Ω loading.
The linear battery charger stores the converted DC power into a battery. Since even small
power saving can be enough to run the low-power PRU, a battery charger with low IvQ is desirable.
The presented battery charger is based on a single amplifier for regulation and the charging
phase transition from the constant-current (CC) phase to the constant-voltage (CV) phase. The
proposed unified amplifier is based on stacked differential pairs which share the bias current. Its
current-steering property removes multiple amplifiers for regulation and the CC-CV transition, and
achieves high unity-gain loop bandwidth for fast regulation. The charger with the maximum charging
current of 25 mA is implemented in 0.35 µm CMOS. A peak charger efficiency of 94% and
average charger efficiency of 88% are achieved with an 80-mAh Li-ion polymer battery.
The second part of this dissertation focuses on analog-to-digital converters (ADCs). From a
signal processing perspective, an ADC is one of the most important circuit blocks in the PRU.
Hence, an energy-efficient ADC is essential in the energy-constrained environment. A pipelined successive
approximation register (SAR) ADC has good energy efficiency in a design space of
moderate-to-high speeds and resolutions. Process-Voltage-Temperature variations of a dynamic
amplifier in the pipelined-SAR ADC is a key design issue. This research presents two dynamic
amplifier architectures for temperature compensation. One is based on a voltage-to-time converter
(VTC) and a time-to-voltage converter (TVC), and the other is based on a temperature-dependent
common-mode detector. The former amplifier is adopted in a 13-bit 10-50 MS/s subranging
pipelined-SAR ADC fabricated in 0.13-µm CMOS. The ADC can operate under the power supply
voltage of 0.8-1.2 V. Figure-of-Merits (FoMs) of 4-11.3 fJ/conversion-step are achieved. The latter
amplifier is also implemented in 0.13-µm CMOS, consuming 0.11 mW at 50 MS/s. Its measured
gain variation is 2.1% across the temperature range of -20°C to 85 °C
Integrated high-voltage switched-capacitor DC-DC converters
The focus of this work is on the integrated circuit (IC) level integration of high-voltage switched-capacitor (SC) converters with the goal of fully integrated power management solutions for system-on-chip (SoC) and system-in-pagage (SiP) applications. The full integration of SC converters provides a low cost and compact power supply solution for modern electronics. Currently, there are almost no fully integrated SC converters with input voltages above 5 V. The purpose of this work is to provide solutions for higher input voltages. The increasing challenges of a compact and efficient power supply on the chip are addressed. High-voltage rated components and the increased losses caused by parasitics not only reduce power density but also efficiency. Loss mechanisms in high-voltage SC converters are investigated resulting in an optimized model for high-voltage SC converters. The model developed allows an appropriate comparison of different semiconductor technologies and converter topologies. Methods and design proposals for loss
reduction are presented. Control of power switches with their supporting circuits is a further challenge for high-voltage SC converters. The aim of this work is to develop fully integrated SC converters with a wide input voltage range. Different topologies and concepts are investigated. The implemented fully integrated SC converter has an input voltage range of 2 V to 13 V. This is twice the range of existing converters. This is achieved by an implemented buck and boost mode as well as 17 conversion ratios. Experimental results show a peak efficiency of 81.5%. This is the highest published peak efficiency for fully integrated SC converters with an input voltage > 5V. With the help of the model developed in this work, a three-phase SC converter topology for input voltages up to 60 V is derived and then investigated and discussed. Another focus of this work is on the power supply of sensor nodes and smart home applications with low-power consumption. Highly integrated micro power supplies that operate directly from mains voltage are particularly suitable for these applications. The micro power supply proposed in this work utilizes the high-voltage SC converter developed. The output power is 14 times higher and the power density eleven times higher than prior work. Since plenty of power switches are built into modern multi-ratio SC converters, the switch control circuits must be optimized with regard to low-power consumption and area requirements. In this work, different level shifter concepts are investigated and a low-power high-voltage level shifter for 50 V applications based on a capacitive level shifter is introduced. The level shifter developed exceeds the state of the art by a factor of more than eleven with a power consumption of 2.1pJ per transition. A propagation delay of 1.45 ns is achieved. The presented high-voltage level shifter is the first level shifter for 50 V applications with a propagation delay below 2 ns and power consumption below 20pJ per transition. Compared to the state of the art, the figure of merit is significantly improved by a factor of two. Furthermore, various charge pump concepts are investigated and evaluated within the context of this work. The charge pump, optimized in this work, improves the state of the art by a factor of 1.6 in terms of efficiency. Bidirectional
switches must be implemented at certain locations within the power stage to prevent reverse conduction. The topology of a bidirectional switch developed in this work reduces the dynamic switching losses by 70% and the area consumption including the required charge pumps by up to 65% compared to the state of the
art. These improvements make it possible to control the power switches in a fast and efficient way.
Index terms — integrated power management, high input voltage, multi-ratio SC converter, level shifter,
bidirectional switch, micro power supplyDer Schwerpunkt dieser Arbeit liegt auf der Erforschung von Switched-Capacitor (SC) Spannungswandler für höhere Eingangsspannungen. Ziel der Arbeit ist es Lösungen für ein voll auf dem Halbleiterchip integriertes Power Management anzubieten um System on Chip (SoC) und System in Package (SiP) zu ermöglichen. Die vollständige Integration von SC Spannungswandlern bietet eine kostengünstige und kompakte Spannungsversorgungslösung für moderne Elektronik. Der kontinuierliche Trend hin zu immer kompakterer Elektronik und hin zu höheren Versorgungsspannungen wird in dieser Arbeit adressiert. Aktuell gibt es sehr wenige voll integrierte SC Spannungswandler mit einer Eingangsspannung größer 5 V. Die mit steigender Spannung zunehmenden Herausforderungen an eine kompakte und effiziente Spannungsversorgung auf dem Chip werden in dieser Arbeit untersucht. Die höhere Spannungsfestigkeit der verwendeten Komponenten korreliert mit erhöhten Verlusten und erhöhtem Flächenverbrauch, welche sich
negativ auf den Wirkungsgrad und die Leistungsdichte von SC Spannungswandlern auswirkt. Bestandteil dieser Arbeit ist die Untersuchung dieser Verlustmechanismen und die Entwicklung eines Modells, welches speziell für höhere Spannungen optimiert wurde. Das vorgestellte Modell ermöglicht zum einen die optimale Dimensionierung der Spannungswandler und zum anderen faire Vergleichsmöglichkeiten zwischen verschiedenen SC Spannungswandler Architekturen und Halbleitertechnologien. Demnach haben sowohl die gewählte Architektur und Halbleitertechnologie als auch die Kombination aus gewählter Architektur und Technologie erheblichen Einfluss auf die Leistungsfähigkeit der Spannungswandler. Ziel dieser Arbeit ist die Vollintegration eines SC Spannungswandlers mit einem weiten und hohen Eingangsspannungsbereich zu
entwickeln. Dazu wurden verschiedene Schaltungsarchitekturen und Konzepte untersucht. Der vorgestellte vollintegrierte SC Spannungswandler weist einen Eingangsspannungsbereich von 2 V bis 13 V auf. Dies ist eine Verdopplung im Vergleich zum Stand der Technik. Dies wird durch einen implementierten Auf- und
Abwärtswandler-Betriebsmodus sowie 17 Übersetzungsverhältnisse erreicht. Experimentelle Ergebnisse zeigen einen Spitzenwirkungsgrad von 81.5%. Dies ist der höchste veröffentlichte Spitzenwirkungsgrad für vollintegrierte SC Spannungswandler mit einer Eingangsspannung größer 5 V. Mit Hilfe des in dieser
Arbeit entwickelten Modells wird eine dreiphasige SC Spannungswandler Architektur für Eingangsspannungen bis zu 60 V entwickelt und anschließend analysiert und diskutiert.
Ein weiterer Schwerpunkt dieser Arbeit adressiert die kompakte Spannungsversorgung von Sensorknoten mit geringem Stromverbrauch, für Anwendungen wie Smart Home und Internet der Dinge (IoT). Für diese Anwendungen eignen sich besonders gut hochintegrierte Mikro-Netzteile, welche direkt mit dem 230VRMS-Hausnetz (bzw. 110VRMS) betrieben werden können. Das in dieser Arbeit vorgestellte Mikro-Netzteil nutzt einen in dieser Arbeit entwickelten SC Spannungswandler für hohe Eingangsspannungen. Die damit erzielte Ausgangsleistung ist 14-mal größer im Vergleich zum Stand der Technik.
In SC Spannungswandlern für hohe Spannungen werden viele Leistungsschalter benötigt, deshalb muss bei der Schalteransteuerung besonders auf einen geringen Leistungsverbrauch und Flächenbedarf der benötigten Schaltungsblöcke geachtet werden. Gegenstand dieser Arbeit ist sowohl die Analyse verschiedener Konzepte
für Pegelumsetzer, als auch die Entwicklung eines stromsparenden Pegelumsetzers für 50 V-Anwendungen. Mit einer Leistungsaufnahme von 2.1pJ pro Signalübergang reduziert der entwickelte Pegelumsetzer mit kapazitiver Kopplung um mehr als elfmal die Leistungsaufnahme im Vergleich zum Stand der Technik. Die erreichte Laufzeitverzögerung beträgt 1.45 ns. Damit erzielt der vorgestellte Hochspannungs-Pegelumsetzer als erster Pegelumsetzer für 50 V-Anwendungen eine Laufzeitverzögerung unter 2 ns und eine Leistungsaufnahme unter 20pJ pro Signalwechsel. Im Vergleich zum Stand der Technik wird die Leistungskennzahl
um den Faktor zwei deutlich verbessert. Darüber hinaus werden im Rahmen dieser Arbeiten verschiedene Ladungspumpenkonzepte untersucht und bewertet. Die in dieser Arbeit optimierte Ladungspumpe verbessert den Stand der Technik um den Faktor 1.6 in Bezug auf den Wirkungsgrad. Die in dieser Arbeit entwickelte Schaltungsarchitektur eines bidirektionalen Schalters reduziert die dynamischen Schaltverluste um 70% und den benötigten Flächenbedarf inklusive der benötigten Ladungspumpe um bis zu 65% gegenüber dem Stand der Technik. Diese Verbesserungen ermöglichen es, die Leistungsschalter schnell und effizient anzusteuern.
Schlagworte — Integriertes Powermanagement, hohe Eingangsspannung, Multi-Ratio SC Spannungswan-
dler, Pegelumsetzer, bidirektionaler Schalter, Mikro-Netztei
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