An Ultra Low Power Digital to Analog Converter Optimized for Small Format LCD Applications

Liquid crystal displays (LCDs) for mobile applications present a unique design challenge. These small format displays can be found primarily in cell phones and PDAs which are devices that have particularly stringent power requirements. At the same time, the displays are increasing in resolution with every generation. This is creating demand for new LCD display technologies. The predominant amorphous thin film transistor technology is no longer feasible in the new high resolution small format screens due to the fact that the displays require too many connections to the driver and the aperture ratios do not allow high density displays. New technologies such as low temperature polysilicon (LTPS) displays continue to shrink in size and increase in resolution. LTPS technology enables the display manufacturer to create relatively high quality transistors on the glass. This allows for a display architecture which integrates the gate driver on the glass. Newer LTPS LCDs also enable a high level of multiplexing the sources lines on the glass which allows for a much simpler connection to the display driver chip. The electronic drivers for these display applications must adhere to strict power and area budgets. This work describes a low-power, area efficient, scalable, digital-to-analog conversion (DAC) integrated circuit architecture optimized for driving small format LCDs. The display driver is based on a twelve channel, 9-bit DAC driver. This architecture, suitable for % VGA resolution displays, exhibited a 2 MSPS conversion rate, less than 300 pW power dissipation per channel using a 5 V supply, and a die area of 0.042 mm per DAC. A new performance standard is set for DAC display drivers in joules per bit areal density

Radio frequency electronics on plastic

In this paper the recent progress of active high frequency electronics on plastic is discussed. This technology is mechanically flexible, bendable, stretchable and does not need any rigid chips. Indium Gallium Zinc Oxide (IGZO) technology is applied. At 2 V supply and gate length of 0.5 μm, the thin-film transistors (TFTs) yield a measured transit frequency of 138 MHz. Our scalable TFT compact simulation model shows good agreement with measurements. To achieve a sufficiently high yield, TFTs with gate lengths of around 5 μm are used for the circuit design. A Cherry Hopper amplifier with 3.5 MHz bandwidth, 10 dB gain and 5 mW dc power is presented. The fully integrated receiver covering a plastic foil area of 3 × 9 mm2 includes a four stage cascode amplifier, an amplitude detector, a baseband amplifier and a filter. At a dc current of 7.2 mA and a supply of 5 V, a bandwidth of 2 - 20 MHz and a gain beyond 15 dB were measured. Finally, an outlook regarding future advancements of high frequency electronics on plastic is given

Design and simulation of a smart bottle with fill-level sensing based on oxide TFT technology

Packaging is an important element responsible for brand growth and one of the main rea-sons for producers to gain competitive advantages through technological innovation. In this re-gard, the aim of this work is to design a fully autonomous electronic system for a smart bottle packaging, being integrated in a European project named ROLL-OUT. The desired application for the smart bottle is to act as a fill-level sensor system in order to determine the liquid content level that exists inside an opaque bottle, so the consumer can exactly know the remaining quantity of the product inside. An in-house amorphous indium–gallium–zinc oxide thin-film transistor (a-IGZO TFT) model, previously developed, was used for circuit designing purposes. This model was based in an artificial neural network (ANN) equivalent circuit approach. Taking into account that only n-type oxide TFTs were used, plenty of electronic building-blocks have been designed: clock generator, non-overlapping phase generator, a capacitance-to-voltage converter and a comparator. As it was demonstrated by electrical simulations, it has been achieved good functionality for each block, having a final system with a power dissipation of 2.3 mW (VDD=10 V) not considering the clock generator. Four printed circuit boards (PCBs) have been also designed in order to help in the testing phase. Mask layouts were already designed and are currently in fabrication, foreseeing a suc-cessful circuit fabrication, and a major step towards the design and integration of complex trans-ducer systems using oxide TFTs technology

Biosensors and CMOS Interface Circuits

abstract: Analysing and measuring of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. Point of care diagnostic system, composing of biosensors, have promising applications for providing cheap, accurate and portable diagnosis. Owing to these expanding medical applications and advances made by semiconductor industry biosensors have seen a tremendous growth in the past few decades. Also emergence of microfluidics and non-invasive biosensing applications are other marker propellers. Analyzing biological signals using transducers is difficult due to the challenges in interfacing an electronic system to the biological environment. Detection limit, detection time, dynamic range, specificity to the analyte, sensitivity and reliability of these devices are some of the challenges in developing and integrating these devices. Significant amount of research in the field of biosensors has been focused on improving the design, fabrication process and their integration with microfluidics to address these challenges. This work presents new techniques, design and systems to improve the interface between the electronic system and the biological environment. This dissertation uses CMOS circuit design to improve the reliability of these devices. Also this work addresses the challenges in designing the electronic system used for processing the output of the transducer, which converts biological signal into electronic signal.Dissertation/ThesisM.S. Electrical Engineering 201

Development of a compact and low-cost weather station for renewable energy applications

This paper describes the development of a weather station integrating several sensors which allows the measurement and data storage of the following environmental parameters: solar irradiance, temperature, humidity, wind speed, and wind direction. The collected data is later transferred to a mobile device, where it is stored in a database and processed in order to be visualized and analyzed by the user. For such purpose, a dedicated mobile app was developed and presented along the paper. The weather station also integrates small solar photovoltaic modules of three different technologies: polycrystalline, monocrystalline and amorphous silicon. Based on that, the weather station also collects information that may be employed to help the user in determining the most suitable solar photovoltaic technology for installation in a particular location. The developed system uses a Bluetooth Low Energy (BLE) wireless network to transfer the data to the mobile device when the user approaches the weather station. The system operation was validated through experimental tests that encompass all the main developed features, from the data acquisition in the weather station, to the visualization in the mobile device.- (undefined

Design and experimental validation of a compact low-cost weather station for solar photovoltaic applications

This paper presents a compact low-cost weather station specially dedicated to renewable energy applications based on solar photovoltaic (PV) technologies. The main objective of the weather station is to verify which technology of solar PV modules would be more suitable for the specific location where the weather station is installed. Therefore, the developed weather station includes three technologies of PV modules (polycrystalline, monocrystalline, and amorphous silicon), each one connected to a dedicated DC-DC power converter with a maximum power point control (MPPC) functionality, as well as a set of sensors (solar irradiance, temperature, humidity, wind speed, and wind direction) used to measure the local weather. The acquired data is processed and stored locally in the weather station and, when necessary, the user can download the data to an Android mobile device through a Bluetooth Low Energy (BLE) wireless network connection using the developed mobile app, where the transferred data is stored in a SQLite database and can be visualized in graphs. Throughout the paper, the design of the developed weather station and the associated technologies are described, as well as the details of the mobile app. The developed system comprising the weather station and the mobile app was validated through a set of experimental tests ranging from the data acquisition to its visualization, as well as the achieved wireless data transfer performance.This work was supported by FCT national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020

Investigation of the Performance of Photon Counting Arrays Based on Polycrystalline Silicon Thin-Film Transistors

Projection x-ray imaging is commonly employed to visualize internal human anatomy and used to produce diagnostic images. Modern projection imaging is typically performed using an active matrix, flat panel imager that is comprised of a converter layer overlying a pixelated array. The images are formed by converting x-ray photons into electrical signals, and then integrating those signals over a frame time – a method referred to as fluence integration. Recently, imagers employing a second method for creating x-ray images – referred to as photon counting – have been developed and used to perform mammographic imaging (a form of projection imaging). Photon counting involves measuring the energy of each interacting x-ray photon and storing digital counts of the number of photons exceeding one or more energy thresholds. Because the imaging information is stored digitally, photon counting imagers are less susceptible to noise than fluence-integrating imagers – which improves image quality and/or decreases the amount of radiation required to acquire an image. Current photon counting mammographic imagers are based on crystalline silicon and are limited in detection area. In order to produce an image, the array is moved in a scanning motion across the object of interest. A photon counting imager with larger detection area would benefit other projection imaging modalities – such as radiography (which produces, for example, chest x-ray images) or fluoroscopy (which is used for non-invasively inserting stents and other medical devices). However, techniques to increase detection area, such as tiling multiple arrays, result in increased imager complexity or cost. For this reason, our group has been exploring the possibility of creating photon counting arrays using a different semiconductor material, referred to as polycrystalline silicon (poly-Si). This material is fabricated using a thin-film process, which allows the economic manufacture of monolithic, large-area arrays and has favorable material properties for creating complex, high speed circuits. Using poly-Si, a set of prototype arrays have been designed and fabricated. The design of the arrays consists of four components: an amplifier, a comparator, a clock generator, and a counter. Several circuit variations were created for each component, and circuit simulations were performed in order to determine energy resolution and count rate values for each variation of each component. For the amplifier component, all circuit variations were determined to have an energy resolution of ~10% when presented with a 70 keV input x-ray photon (a typical photon energy level used in diagnostic imaging). This energy resolution value is comparable to those reported for photon counting imagers fabricated using crystalline silicon. In addition, while count rate values for the amplifier component were roughly one order of magnitude too low for radiographic and fluoroscopic applications (which require count rates on the order of 1 million counts per second per square millimeter [cps/mm2]), a hypothetical amplifier circuit variation with count rate capabilities suitable for these applications (while preserving the same ~10% energy resolution) was designed. In addition, the count rate values for the various comparator, clock generator, and counter circuit variations ranged from 100 to 3000 kcps/mm2. Finally, due to improvements in the poly-Si fabrication process (driven largely by the display industry), future photon counting arrays employing this material can have pixel pitches as small as 250 um – a size approaching that suitable for radiographic and fluoroscopic imaging.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144006/1/akliang_1.pd

Device-circuit interactions and impact on TFT circuit-system design

This paper reviews the importance of device-circuit interactions (DCI) and its consideration when designing thin film transistor circuits and systems. We examine temperature- and process-induced variations and propose a way to evaluate the maximum achievable intrinsic performance of the TFT. This is aimed at determining when DCI becomes crucial for a specific application. Compensation methods are then reviewed to show examples of how DCI is considered in the design of AMOLED displays. Other designs such as analog front-end and image sensors are also discussed, where alternate circuits should be designed to overcome the limitations of the intrinsic device properties

The Conference on High Temperature Electronics

The status of and directions for high temperature electronics research and development were evaluated. Major objectives were to (1) identify common user needs; (2) put into perspective the directions for future work; and (3) address the problem of bringing to practical fruition the results of these efforts. More than half of the presentations dealt with materials and devices, rather than circuits and systems. Conference session titles and an example of a paper presented in each session are (1) User requirements: High temperature electronics applications in space explorations; (2) Devices: Passive components for high temperature operation; (3) Circuits and systems: Process characteristics and design methods for a 300 degree QUAD or AMP; and (4) Packaging: Presently available energy supply for high temperature environment