Efficient Ultra High Voltage Controller Based Complementary Metal Oxide Semiconductor Switched Capacitor DC-DC Converter For Radio Frequency Micro Electro Mechanical Systems Switch Actuation

Achieving wireless connectivity in ever smaller, lower power portable devices with increasing number of features and better radio-frequency (RF) performance is becoming difficult to fulfill through existing RF front-end technology. RF micro-electro-mechanical systems (MEMS) switch technology, which has significantly better RF characteristics than conventional technology and has near-zero power consumption, is one of the emerging solutions for next generation RF front-ends. However, to achieve satisfactory RF MEMS device performance, it is often necessary to have an actuating circuitry to generate high direct current (DC) voltages for device actuation with low power consumption. In this study, the authors present an RF MEMS switch controller based on a switched-capacitor (SC) DC-DC converter in a 0.35 μm CMOS technology. In this design, novel design techniques for a higher output voltage and lower power consumption in a smaller die area are proposed. The authors demonstrate the design of the high-voltage (HV) SC DC-DC converter by using low-voltage transistors and address reliability issues in the design. Through the proposed design techniques, the SC DC-DC converter achieves more than 25% higher boosted voltage compared to converters that use HV transistors. The proposed design provides 40% power reduction through the charge recycling circuit. Moreover, the SC DC-DC converter achieves 45% smaller than the area of the conventional converter

RF MEMS reference oscillators platform for wireless communications

A complete platform for RF MEMS reference oscillator is built to replace bulky quartz from mobile devices, thus reducing size and cost. The design targets LTE transceivers. A low phase noise 76.8 MHz reference oscillator is designed using material temperature compensated AlN-on-silicon resonator. The thesis proposes a system combining piezoelectric resonator with low loading CMOS cross coupled series resonance oscillator to reach state-of-the-art LTE phase noise specifications. The designed resonator is a two port fundamental width extensional mode resonator. The resonator characterized by high unloaded quality factor in vacuum is designed with low temperature coefficient of frequency (TCF) using as compensation material which enhances the TCF from - 3000 ppm to 105 ppm across temperature ranges of -40˚C to 85˚C. By using a series resonant CMOS oscillator, phase noise of -123 dBc/Hz at 1 kHz, and -162 dBc/Hz at 1MHz offset is achieved. The oscillator’s integrated RMS jitter is 106 fs (10 kHz–20 MHz), consuming 850 μA, with startup time is 250μs, achieving a Figure-of-merit (FOM) of 216 dB. Electronic frequency compensation is presented to further enhance the frequency stability of the oscillator. Initial frequency offset of 8000 ppm and temperature drift errors are combined and further addressed electronically. A simple digital compensation circuitry generates a compensation word as an input to 21 bit MASH 1 -1-1 sigma delta modulator incorporated in RF LTE fractional N-PLL for frequency compensation. Temperature is sensed using low power BJT band-gap front end circuitry with 12 bit temperature to digital converter characterized by a resolution of 0.075˚C. The smart temperature sensor consumes only 4.6 μA. 700 MHz band LTE signal proved to have the stringent phase noise and frequency resolution specifications among all LTE bands. For this band, the achieved jitter value is 1.29 ps and the output frequency stability is 0.5 ppm over temperature ranges from -40˚C to 85˚C. The system is built on 32nm CMOS technology using 1.8V IO device

CMOS Closed-loop Control of MEMS Varactors

A closed-loop capacitance sensing and control mix-mode circuit with a dedicated sensor electrode and a proportional-integral controller was designed for MEMS varactors. The control was based on tuning the bias magnitude of the MEMS varactor according to

Ultra-low Power Circuits for Internet of Things (IOT)

Miniaturized sensor nodes offer an unprecedented opportunity for the semiconductor industry which led to a rapid development of the application space: the Internet of Things (IoT). IoT is a global infrastructure that interconnects physical and virtual things which have the potential to dramatically improve people's daily lives. One of key aspect that makes IoT special is that the internet is expanding into places that has been ever reachable as device form factor continue to decreases. Extremely small sensors can be placed on plants, animals, humans, and geologic features, and connected to the Internet. Several challenges, however, exist that could possibly slow the development of IoT. In this thesis, several circuit techniques as well as system level optimizations to meet the challenging power/energy requirement for the IoT design space are described. First, a fully-integrated temperature sensor for battery-operated, ultra-low power microsystems is presented. Sensor operation is based on temperature independent/dependent current sources that are used with oscillators and counters to generate a digital temperature code. Second, an ultra-low power oscillator designed for wake-up timers in compact wireless sensors is presented. The proposed topology separates the continuous comparator from the oscillation path and activates it only for short period when it is required. As a result, both low power tracking and generation of precise wake-up signal is made possible. Third, an 8-bit sub-ranging SAR ADC for biomedical applications is discussed that takes an advantage of signal characteristics. ADC uses a moving window and stores the previous MSBs voltage value on a series capacitor to achieve energy saving compared to a conventional approach while maintaining its accuracy. Finally, an ultra-low power acoustic sensing and object recognition microsystem that uses frequency domain feature extraction and classification is presented. By introducing ultra-low 8-bit SAR-ADC with 50fF input capacitance, power consumption of the frontend amplifier has been reduced to single digit nW-level. Also, serialized discrete Fourier transform (DFT) feature extraction is proposed in a digital back-end, replacing a high-power/area-consuming conventional FFT.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137157/1/seojeong_1.pd

CMOS systems and circuits for sub-degree per hour MEMS gyroscopes

The objective of our research is to develop system architectures and CMOS circuits that interface with high-Q silicon microgyroscopes to implement navigation-grade angular rate sensors. The MEMS sensor used in this work is an in-plane bulk-micromachined mode-matched tuning fork gyroscope (M² – TFG ), fabricated on silicon-on-insulator substrate. The use of CMOS transimpedance amplifiers (TIA) as front-ends in high-Q MEMS resonant sensors is explored. A T-network TIA is proposed as the front-end for resonant capacitive detection. The T-TIA provides on-chip transimpedance gains of 25MΩ, has a measured capacitive resolution of 0.02aF /√Hz at 15kHz, a dynamic range of 104dB in a bandwidth of 10Hz and consumes 400μW of power. A second contribution is the development of an automated scheme to adaptively bias the mechanical structure, such that the sensor is operated in the mode-matched condition. Mode-matching leverages the inherently high quality factors of the microgyroscope, resulting in significant improvement in the Brownian noise floor, electronic noise, sensitivity and bias drift of the microsensor. We developed a novel architecture that utilizes the often ignored residual quadrature error in a gyroscope to achieve and maintain perfect mode-matching (i.e.0Hz split between the drive and sense mode frequencies), as well as electronically control the sensor bandwidth. A CMOS implementation is developed that allows mode-matching of the drive and sense frequencies of a gyroscope at a fraction of the time taken by current state of-the-art techniques. Further, this mode-matching technique allows for maintaining a controlled separation between the drive and sense resonant frequencies, providing a means of increasing sensor bandwidth and dynamic range. The mode-matching CMOS IC, implemented in a 0.5μm 2P3M process, and control algorithm have been interfaced with a 60μm thick M2−TFG to implement an angular rate sensor with bias drift as low as 0.1°/hr ℃ the lowest recorded to date for a silicon MEMS gyro.Ph.D.Committee Chair: Farrokh Ayazi; Committee Member: Jennifer Michaels; Committee Member: Levent Degertekin; Committee Member: Paul Hasler; Committee Member: W. Marshall Leac

Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

Power Management ICs for Internet of Things, Energy Harvesting and Biomedical Devices

This dissertation focuses on the power management unit (PMU) and integrated circuits (ICs) for the internet of things (IoT), energy harvesting and biomedical devices. Three monolithic power harvesting methods are studied for different challenges of smart nodes of IoT networks. Firstly, we propose that an impedance tuning approach is implemented with a capacitor value modulation to eliminate the quiescent power consumption. Secondly, we develop a hill-climbing MPPT mechanism that reuses and processes the information of the hysteresis controller in the time-domain and is free of power hungry analog circuits. Furthermore, the typical power-performance tradeoff of the hysteresis controller is solved by a self-triggered one-shot mechanism. Thus, the output regulation achieves high-performance and yet low-power operations as low as 12 µW. Thirdly, we introduce a reconfigurable charge pump to provide the hybrid conversion ratios (CRs) as 1⅓× up to 8× for minimizing the charge redistribution loss. The reconfigurable feature also dynamically tunes to maximum power point tracking (MPPT) with the frequency modulation, resulting in a two-dimensional MPPT. Therefore, the voltage conversion efficiency (VCE) and the power conversion efficiency (PCE) are enhanced and flattened across a wide harvesting range as 0.45 to 3 V. In a conclusion, we successfully develop an energy harvesting method for the IoT smart nodes with lower cost, smaller size, higher conversion efficiency, and better applicability. For the biomedical devices, this dissertation presents a novel cost-effective automatic resonance tracking method with maximum power transfer (MPT) for piezoelectric transducers (PT). The proposed tracking method is based on a band-pass filter (BPF) oscillator, exploiting the PT’s intrinsic resonance point through a sensing bridge. It guarantees automatic resonance tracking and maximum electrical power converted into mechanical motion regardless of process variations and environmental interferences. Thus, the proposed BPF oscillator-based scheme was designed for an ultrasonic vessel sealing and dissecting (UVSD) system. The sealing and dissecting functions were verified experimentally in chicken tissue and glycerin. Furthermore, a combined sensing scheme circuit allows multiple surgical tissue debulking, vessel sealer and dissector (VSD) technologies to operate from the same sensing scheme board. Its advantage is that a single driver controller could be used for both systems simplifying the complexity and design cost. In a conclusion, we successfully develop an ultrasonic scalpel to replace the other electrosurgical counterparts and the conventional scalpels with lower cost and better functionality

Charge pumps and floating gate devices for switching applications

On-chip impedance tuning is used to overcome IC perturbations caused by packaging stress. Tuning is more important for matching networks of radio frequency (RF) systems. Possible package resonance and fabrication process variations may cause instability, which is a major problem in RF systems. Thus, precautions need to be taken in order to maintain the overall stability of components and the final system itself. Electrically erasable programmable read-only memory switches (EEPROMs) occupy less die area compared to e-fuses and microelectromechanical system (MEMS) switches, thus EEPROMs are proposed to be used as tuning switches in millimetre-wave (mm-wave) applications. It is anticipated that EEPROM switches will also enable multi-time programming because of the smaller area and the fact that more switches can be used for fine-tuning. The problem addressed in this research is how suitable EEPROMs are for switching applications in the mm-wave region. The main focus of this dissertation is to characterise the suitability of EEPROM switches qualitatively for tuning with systems operating in the mm-wave spectrum. 130 nm SiGe BiCMOS IBM 8HP process technology was used for simulation and the fabricated prototypes. The Dickson charge pump (CP), two voltage doubler CPs and four floating gate (FG) devices were investigated. Literature and theoretical verification was done using computer aided design (CAD) Cadence software through circuit analysis and the layouts were also designed for integrated circuit (IC) prototype fabrication. The qualitative evaluation of the hypothesis was based on investigating reliability issues, switching characteristics, CP output drive capability and mm-wave characterisation. The maximum measured drain current for FGs was 1.4 mA, 2.7 mA and 3 mA for devices 2, 3 and 4, respectively. The ratio between ON state switching current (after tunnelling) and OFF state switching current (after injection) was 1.5, 1.35 and 6 for devices 2, 3 and 4, respectively. The ratios correlated with the expected results in terms of FG transistor area: a high area results in a higher ratio. Despite the correlation, devices 2 and 3 may be unsuitable because the ratio is less than 2: a smaller ratio between the ON and OFF states could also result in higher losses. The Dickson CP achieved an output voltage of 2.96 V from an input of 1.2 V compared to 3.08 V as computed from the theoretical analysis and 4.5 V from the simulation results. The prototypes of the voltage doubler CP did not perform as expected: a maximum of 1 V was achieved compared to 4.1 – 5 V as in the simulation results. The suitability of FG devices for switching applications depends on the ratio of the ON and OFF states (associated to insertion and isolation losses): the larger the FG transistor area, the higher the ratio. The reliability issues are dominated by the oxide thickness of the transistor, which contributes to charge leakages and charge trapping: smaller transistor length causes more uncertainties. Charge trapping in the oxide increases the probability of leakages and substrate conduction, thus introduces more losses. Based on the findings of this research work, the FG devices promise to be suitable for mm-wave switching applications and there is a need for further research investigation to characterise the devices in the mm-wave region fully. AFRIKAANS : Impedansie-instelling op skyf word gebruik om steurings in geïntegreerde stroombane wat deur verpakkingstres veroorsaak word, te oorkom. Instelling is meer belangrik om netwerke van radiofrekwensiesisteme te paar. Moontlike verpakkingresonansie en variasies in die vervaardigingsproses kan onstabiliteit veroorsaak, wat ‟n groot probleem is in radiofrekwensiesisteme. Voorsorg moet dus getref word om die oorhoofse stabiliteit van komponente en die finale sisteem self te handhaaf. Elektries uitveebare programmeerbare slegs-lees-geheueskakelaars (EEPROMs) neem minder matrysarea op as e-sekerings en die sekerings van mikro-elektromeganiese sisteme en word dus voorgestel vir gebruik as instellingskakelaars in millimetergolfaanwendings. Daar word verwag dat EEPROM-skakelaars ook multi-tydprogrammering sal moontlik maak as gevolg van die kleiner area en die feit dat meer skakelaars gebruik kan word vir fyn instellings. Die probleem wat in hierdie navorsing aandag geniet, is die geskiktheid van EEPROMS vir skakelaanwendings in die millimetergolfstreek. The hooffokus van die verhandeling is om die geskiktheid van EEPROM-skakelaars kwalitatief te karakteriseer vir instelling met sisteme wat in die millimetergolfspektrum funksioneer. Department of Electrical, Electronic and Computer Engineering v University of Pretoria 130 nm SiGe BiCMOS IBM 8HP-prosestegnologie is gebruik vir simulasie en die vervaardigde prototipes. Die Dickson-laaipomp is gebruik vir simulasie en die vervaardigde prototipes. Die Dickson-laaipomp, twee spanningverdubbelinglaaipompe en vier swewendehektoestelle is ondersoek. Literatuur- en teoretiese verifikasie is gedoen met behulp van rekenaarondersteunde-ontwerp (CAD) Cadence-sagteware deur stroombaananalise en die uitleg is ook ontwerp vir die vervaardiging van geïntegreerdestroombaanprototipes. Die kwalitatiewe evaluasie van die hipotese is gebaseer op die ondersoek van betroubaarheidkwessies, skakelingeienskappe, laaipompuitsetdryfvermoë en millimetergolfkarakterisering. Die maksimum gemete dreineerstroom vir swewende hekke was 1.4 mA, 2.7 mA en 3 mA vir onderskeidelik toestelle 2, 3 en 4. Die verhouding tussen die AAN-toestand van die skakelstroom (na tonnelling) en die AF-toestand van die skakelstroom (na inspuiting) was 1.5, 1.35 en 6 vir toestelle 2, 3 en 4, onderskeidelik. Die verhoudings het ooreengestem met die verwagte resultate rakende die swewendehek-transistorareas: ‟n groot area het ‟n hoër verhouding tot gevolg. Nieteenstaande die ooreenstemming, mag toestelle 2 en 3 moontlik nie geskik wees nie, omdat die verhouding kleiner as 2 is: ‟n kleiner verhouding tussen die AAN- en AF-toestande mag ook hoër verliese tot gevolg hê. Die Dickson-laaipomp het ‟n uitsetspanning van 2.96 V vanaf ‟n inset van 1.2 V vergeleke met 3.08 V soos bereken volgens die teoretiese analise en 4.5 V volgens die simulasieresultate. Die prototipes van die spanningverdubbelinglaaipomp het nie gefunksioneer soos verwag is nie: ‟n maksimum van 1 V is bereik vergeleke met 4.1 – 5 V soos in die simulasieresultate. Die geskiktheid van swewendehektoestelle vir skakelingtoepassings hang af van die verhouding van die AAN- en AF-toestande (wat met invoer-en isolasieverlies geassosieer word): hoe groter die swewendehektransistorarea, hoe hoër die verhouding. Die betroubaarheidkwessies word oorheers deur die oksieddikte van die transistor, wat bydra tot ladinglekkasies en ladingvasvangs: korter transistorlengte veroorsaak meer onsekerheid. Ladingvasvangs in die oksied verhoog die moontlikheid van lekkasies en substraatgeleiding en veroorsaak dus groter verlies. Die bevindings van hierdie navorsing toon dat swewendehektoestelle waarskynlik geskik is vir millimetergolfaanwendings en verdere navorsing is nodig om die toestelle volledig in die millimetergolfstreek te karakteriseer. CopyrightDissertation (MEng)--University of Pretoria, 2013.Electrical, Electronic and Computer Engineeringunrestricte

Integrated interface electronics for capacitive MEMS inertial sensors

This thesis is composed of 13 publications and an overview of the research topic, which also summarizes the work. The research presented in this thesis concentrates on integrated circuits for the realization of interface electronics for capacitive MEMS (micro-electro-mechanical system) inertial sensors, i.e. accelerometers and gyroscopes. The research focuses on circuit techniques for capacitive detection and actuation and on high-voltage and clock generation within the sensor interface. Characteristics of capacitive accelerometers and gyroscopes and the electronic circuits for accessing the capacitive information in open- and closed-loop configurations are introduced in the thesis. One part of the experimental work, an accelerometer, is realized as a continuous-time closed-loop sensor, and is capable of achieving sub-micro-g resolution. The interface electronics is implemented in a 0.7-µm high-voltage technology. It consists of a force feedback loop, clock generation circuits, and a digitizer. Another part of the experimental work, an analog 2-axis gyroscope, is optimized not only for noise, but predominantly for low power consumption and a small chip area. The implementation includes a pseudo-continuous-time sense readout, analog continuous-time drive loop, phase-locked loop (PLL) for clock generation, and high-voltage circuits for electrostatic excitation and high-voltage detection. The interface is implemented in a 0.35-µm high-voltage technology within an active area of 2.5 mm². The gyroscope achieves a spot noise of 0.015 °/s/√H̅z̅ for the x-axis and 0.041 °/s/√H̅z̅ for the y-axis. Coherent demodulation and discrete-time signal processing are often an important part of the sensors and also typical examples that require clock signals. Thus, clock generation within the sensor interfaces is also reviewed. The related experimental work includes two integrated charge pump PLLs, which are optimized for compact realization but also considered with regard to their noise performance. Finally, this thesis discusses fully integrated high-voltage generation, which allows a higher electrostatic force and signal current in capacitive sensors. Open- and closed-loop Dickson charge pumps and high-voltage amplifiers have been realized fully on-chip, with the focus being on optimizing the chip area and on generating precise spurious free high-voltage signals up to 27 V