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

Development of Gate-Controlled DC Electrokinetic Micropumps

Lab-on-chip (LOC) devices have received considerable attention in research and development for automated, high-throughput biological and chemical analysis. While much progress has been accomplished; however, fluid flow control still needs improvement and reminds one of the significant challenges for the future practical LOC devices. This thesis explores the application of electroosmosis (EO) technique and field effect flow control (FEFC) technology for micropumps, an important microfluidic component of LOC systems. In this work, electroosmosis method was employed to electro-kinetically move the working fluid under a longitudinal electric field, and the FEFC technique was also utilized to manipulate the Electroosmotic Flow (EOF) through applying a normal electric field to influence the surface charge at the fluid-microchannel wall interface for an independent control over the EOF. Major accomplishments in this thesis are, study on channel geometry effect with no gate control component, and a single microchannel with gate control component. A number of micropumps with different channel geometries were fabricated using soft lithography technique. PDMS prepolymer served as a top wall and both side walls of the microchannel, with a glass slide as the bottom (in the case of gate control, Indium Tin Oxide glass slides were used). On the gate control region, through adjusting the secondary electric field over the gate, FEFC can locally manipulate EOF. It helps produce a range of flow rates, enhance flow rates, and control flow direction. Moreover, micropumps were interfaced with another microchannel section for sample delivery. To improve the microfluidic device, electro-fluid flow models were developed to describe and predict electric field distribution, velocity field distribution, flow direction, and FEFC phenomena using Finite Element Analysis tool (FEMLAB). The simulation results agreed well with experimental results

Fully superconducting rectifiers and fluxpumps Part 1: Realized methods for pumping flux

The magnetic and electrical properties of superconductors were a challenge for many inventors and designers to use superconducting materials in the construction of fully superconducting voltage and current sources commonly called fluxpumps. In the past twenty years a large variety of mechanically or electrically driven devices have been proposed and successfully operated.\ud \ud In this review the basic principle of operation of each class of devices is shown and specific material problems and limitations are reported. The review will be published in two parts.\ud \ud Part 1 deals with mechanical devices such as flux compressors and dynamos. Although those devices must have been of great importance for technical application, their construction and operation offered great experience with regard to the properties of superconducting materials, their joint techniques switching and mechanical and magnetic stability under ac and dc conditions.\ud \ud In this part also a start is made with the more promising class of electrically driven rectifier fluxpumps. With these rectifiers, current levels over 10 kA can be obtained with high efficiency

High voltage bias waveform generator for an RF MEMS microswitch

An integrated high voltage bias driver for a Radio Frequency Micro-Electro-Mechanical System (RF MEMS) microswitch is proposed. The design and implementation in a 0.7mum integrated circuit process with high and low voltage transistors is shown along with tested results. High voltage Double-Diffused Metal Oxide Semiconductor (DMOS) transistors in combination with low voltage digital logic provide a non-linear solution that achieves rise and fall times of 1mus while keeping power use to a minimum. System design and tradeoffs are presented for alternate approaches and combinations as well as future integration with Direct Current--Direct Current (DC-DC) voltage conversion and an internally generated clock

Integrated DC-DC boost converters using CMOS silicon on Sapphire Technology

With the recent advancements in semiconductor manufacturing towards smaller, faster and more efficient microelectronic systems, the problems of increasing leakage current and reduced breakdown voltage in bulk-CMOS transistors have become substantial in the sub-100-nanometer era. The Peregrine UltraCMOS Silicon-on-Sapphire (SOS) technology that uses highly-insulating sapphire substrate as insulator was introduced to meet the continually growing need for higher performance RF products. The electrically isolated circuit elements in the UltraCMOS technology lead to increased switching speeds and lower power consumption due to reduced junction and parasitic capacitances. Furthermore, the growing need for high-speed switching applications such as boosting a lower voltage level to a higher one gives the UltraCMOS technology an upper hand over the bulk-CMOS process. The limitation to using an UltraCMOS transistor is that its maximum drain to source voltage (VDS ) swing is 2.5V. This thesis aims to address this limitation by studying and implementing various stacking techniques in high power switching applications where voltage switching of higher than 2.5V are required. Fully-integrated DC to DC boost converters with switching circuits based on dynamically self-biased stacked transistors are proposed. For high voltage and high power handling, the proposed stacking techniques equally distribute the overall output voltage to less than 2.5V across each stacked transistor in the switch (V DS of 2.5V)

Load sensitive stable current source for complex precision pulsed electroplating

Electrodeposition is a highly versatile and well explored technology. However, it also depends strongly on the experience level of the operator. This experience includes the pretreatment of the sample, and the composition of the electrolyte settings of the plating parameters. Accurate control over the electroplating current is needed especially for the formation of small structures, where pulsed electrodeposition has proven to reduce many unwanted effects. To bring precision into the formation of optimal recipes, a highly flexible current source based on a microcontroller was developed. It allows a large variety of pulse waveforms, as well as maintaining a feedback loop that controls the current and monitors the output voltage, allowing for both galvanostatic (current driven) and potentiostatic (voltage driven) electrodeposition. The system has been implemented with multiple channels, permitting the simultaneous electrodeposition of multiple substrates in parallel. Being based on a microcomputer, the system can be programmed using predefined recipes individually for each channel, or even adapt the recipes during plating. All measurement values are continuously recorded for the purpose of documentation and diagnosis. The current source is based on a high power operational amplifier in a modified Howland current source configuration. This paper describes the functionality of the electrodeposition system, with a focus on the stability of the source current under different electrodeposition current densities and frequencies. The performance and high capability of the system is demonstrated by performing and analyzing two nontrivial plating applications

Low-Power Energy Efficient Circuit Techniques for Small IoT Systems

Although the improvement in circuit speed has been limited in recent years, there has been increased focus on the internet of things (IoT) as technology scaling has decreased circuit size, power usage and cost. This trend has led to the development of many small sensor systems with affordable costs and diverse functions, offering people convenient connection with and control over their surroundings. This dissertation discusses the major challenges and their solutions in realizing small IoT systems, focusing on non-digital blocks, such as power converters and analog sensing blocks, which have difficulty in following the traditional scaling trends of digital circuits. To accommodate the limited energy storage and harvesting capacity of small IoT systems, this dissertation presents an energy harvester and voltage regulators with low quiescent power and good efficiency in ultra-low power ranges. Switched-capacitor-based converters with wide-range energy-efficient voltage-controlled oscillators assisted by power-efficient self-oscillating voltage doublers and new cascaded converter topologies for more conversion ratio configurability achieve efficient power conversion down to several nanowatts. To further improve the power efficiency of these systems, analog circuits essential to most wireless IoT systems are also discussed and improved. A capacitance-to-digital sensor interface and a clocked comparator design are improved by their digital-like implementation and operation in phase and frequency domain. Thanks to the removal of large passive elements and complex analog blocks, both designs achieve excellent area reduction while maintaining state-of-art energy efficiencies. Finally, a technique for removing dynamic voltage and temperature variations is presented as smaller circuits in advanced technologies are more vulnerable to these variations. A 2-D simultaneous feedback control using an on-chip oven control locks the supply voltage and temperature of a small on-chip domain and protects circuits in this locked domain from external voltage and temperature changes, demonstrating 0.0066 V/V and 0.013 °C/°C sensitivities to external changes. Simple digital implementation of the sensors and most parts of the control loops allows robust operation within wide voltage and temperature ranges.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138743/1/wanyeong_1.pd