Variability-aware design of CMOS nanopower reference circuits

Questo lavoro è inserito nell'ambito della progettazione di circuiti microelettronici analogici con l'uso di tecnologie scalate, per le quali ha sempre maggiore importanza il problema della sensibilità delle grandezze alle variazioni di processo. Viene affrontata la progettazione di generatori di quantità di riferimento molto precisi, basati sull’uso di dispositivi che sono disponibili anche in tecnologie CMOS standard e che sono “intrinsecamente” più robusti rispetto alle variazioni di processo. Questo ha permesso di ottenere una bassa sensibilità al processo insieme ad un consumo di potenza estremamente ridotto, con il principale svantaggio di una elevata occupazione di area. Tutti i risultati sono stati ottenuti in una tecnologia 0.18μm CMOS. In particolare, abbiamo progettato un riferimento di tensione, ottenendo una deviazione standard relativa della tensione di riferimento dello 0.18% e un consumo di potenza inferiore a 70 nW, sulla base di misure su un set di 20 campioni di un singolo batch. Sono anche disponibili risultati relativi alla variabilità inter batch, che mostrano una deviazione standard relativa cumulativa della tensione di riferimento dello 0.35%. Abbiamo quindi progettato un riferimento di corrente, ottenendo anche in questo caso una sensibilità al processo della corrente di riferimento dell’1.4% con un consumo di potenza inferiore a 300 nW (questi sono risultati sperimentali ottenuti dalle misure su 20 campioni di un singolo batch). I riferimenti di tensione e di corrente proposti sono stati quindi utilizzati per la progettazione di un oscillatore a rilassamento a bassa frequenza, che unisce una ridotta sensibilità al processo, inferiore al 2%, con un basso consumo di potenza, circa 300 nW, ottenuto sulla base di simulazioni circuitali. Infine, nella progettazione dei blocchi sopra menzionati, abbiamo applicato un metodo per la determinazione della stabilità dei punti di riposo, basato sull’uso dei CAD standard utilizzati per la progettazione microelettronica. Questo approccio ci ha permesso di determinare la stabilità dei punti di riposo desiderati, e ci ha anche permesso di stabilire che i circuiti di start up spesso non sono necessari

Digital-Based Analog Processing in Nanoscale CMOS ICs for IoT Applications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Examining hydration status and the physiological and behavioural influences on voluntary water intake

Understanding the physiological and behavioural reasons that result in voluntary water intake and the volume subsequently consumed in both the work place and during and following an exercise setting can provide further information on water balance and the necessity and requirements of water intake. The first study (Chapter 3) aimed to assess hydration status in the adult population at the start and end of a working day and the amount of water from beverages that was consumed. Urine osmolality and urine specific gravity (USG) suggested a large proportion of subjects arrived (osmolality: 54%; USG: 53%) and left (osmolality: 35%; USG: 33%) work in a hypohydrated state, with variation between subjects in the same and different places of work. Reported water intake varied between groups with males consuming more than females. To further examine hydration status it was proposed to assess the use of capillary blood sampling as an alternative to more restrictive venous blood sampling (Chapter 4), however, despite tracking changes in blood parameters in a similar capacity, the inconsistencies of results suggested capillary blood sampling could not be used reliably. The remaining chapters in the thesis examined voluntary water intake. In Chapter 5 this was during and following exercise in the cold. Less water was consumed compared to exercise in a warm environment and there was an indication of a blunted thirst response in the cold. Following high intensity intermittent exercise, more water was voluntarily consumed during a one hour recovery period compared to when continuous exercise of the same average power output was performed (Chapter 6). Following exercise there was increased serum osmolality, serum sodium concentration, plasma vasopressin concentration and blood lactate concentration compared to baseline values. The relative contribution that decreasing blood lactate concentrations and water intake during the recovery period had on serum osmolality could not be determined, so the study in Chapter 7 was carried out. The time period during which voluntary water intake was allowed was manipulated during a recovery period following a period of high intensity intermittent exercise. Allowing water intake for the full hour, the final 30 minutes or not at all, resulted in similar decreases in serum osmolality throughout the duration of the recovery period. A combination of finishing the period of exercise allowing plasma volume restoration, reduction in blood lactate concentration, reduction in serum sodium concentration, a restoration of blood lactate concentration and water intake appeared to contribute to decreased serum osmolality. Sensations of thirst were the main stimulants of voluntary water intake (Chapters 3, 5, 6 and 7), however, following exercise, sensations of thirst resulted in water consumption despite the majority of subjects not losing enough water (>2% body mass loss) to require additional rehydration. In this thesis, it can be concluded that voluntary water intake differs between individuals, between work environments, during and following exercise in different environments and following different exercise intensities. Water intake is generally initiated by sensations of thirst arising from physiological and behavioural mechanisms even in the absence of significant hypohydration and will reduce once satiated

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

ULTRA ENERGY-EFFICIENT SUB-/NEAR-THRESHOLD COMPUTING: PLATFORM AND METHODOLOGY

Ph.DDOCTOR OF PHILOSOPH

In Situ Automatic Analog Circuit Calibration and Optimization

As semiconductor technology scales down, the variations of active/passive device characteristics after fabrication are getting more and more significant. As a result, many circuits need more accuracy margin to meet minimum accuracy specifications over huge process-voltage-temperature (PVT) variations. Although, overdesigning a circuit is sometimes not a feasible option because of excessive accuracy margin that requires high power consumption and large area. Consequently, calibration/tuning circuits that can automatically detect and compensate the variations have been researched for analog circuits to make better trade-offs among accuracy, power consumption, and area. The first part of this dissertation shows that a newly proposed in situ calibration circuit for a current reference can relax the sharp trade-off between the temperature coefficient accuracy and the power consumption of the current reference. Prototype chips fabricated in a 180 nm CMOS technology generate 1 nA and achieve an average temperature coefficient of 289 ppm/°C and an average line sensitivity of 1.4 %/V with no help from a multiple-temperature trimming. Compared with other state-of-the-art current references that do not need a multiple-temperature trimming, the proposed circuit consumes at least 74% less power, while maintaining similar or higher accuracy. The second part of this dissertation proves that a newly proposed multidimensional in situ analog circuit optimization platform can optimize a Tow-Thomas bandpass biquad. Unlike conventional calibration/tuning approaches, which only handle one or two frequency-domain characteristics, the proposed platform optimizes the power consumption, frequency-, and time-domain characteristics of the biquad to make a better trade-off between the accuracy and the power consumption of the biquad. Simulation results show that this platform reduces the gain-bandwidth product of op-amps in the biquad by 80% while reducing the standard deviations of frequency- and time-domain characteristics by 82%. Measurement results of a prototype chip fabricated in a 180 nm CMOS technology also show that this platform can save maximum 71% of the power consumption of the biquad while the biquad maintains its frequency-domain characteristics: Q, ωO and the gain at ωO

CMOS Hyperbolic Sine ELIN filters for low/audio frequency biomedical applications

Hyperbolic-Sine (Sinh) filters form a subclass of Externally-Linear-Internally-Non- Linear (ELIN) systems. They can handle large-signals in a low power environment under half the capacitor area required by the more popular ELIN Log-domain filters. Their inherent class-AB nature stems from the odd property of the sinh function at the heart of their companding operation. Despite this early realisation, the Sinh filtering paradigm has not attracted the interest it deserves to date probably due to its mathematical and circuit-level complexity. This Thesis presents an overview of the CMOS weak inversion Sinh filtering paradigm and explains how biomedical systems of low- to audio-frequency range could benefit from it. Its dual scope is to: consolidate the theory behind the synthesis and design of high order Sinh continuous–time filters and more importantly to confirm their micro-power consumption and 100+ dB of DR through measured results presented for the first time. Novel high order Sinh topologies are designed by means of a systematic mathematical framework introduced. They employ a recently proposed CMOS Sinh integrator comprising only p-type devices in its translinear loops. The performance of the high order topologies is evaluated both solely and in comparison with their Log domain counterparts. A 5th order Sinh Chebyshev low pass filter is compared head-to-head with a corresponding and also novel Log domain class-AB topology, confirming that Sinh filters constitute a solution of equally high DR (100+ dB) with half the capacitor area at the expense of higher complexity and power consumption. The theoretical findings are validated by means of measured results from an 8th order notch filter for 50/60Hz noise fabricated in a 0.35μm CMOS technology. Measured results confirm a DR of 102dB, a moderate SNR of ~60dB and 74μW power consumption from 2V power supply

Development and integration of environmental evaluation tools for the ecodesign of sustainable processes and products

Industry is recognized as one of the main sources of environmental pollution and resource depletion, both causing environmental degradation; nonetheless, its contribution to development and wealth creation is also acknowledged. Therefore, the identification of sustainable options in this area is a key factor. Nowadays, the attitude towards pollution prevention and control and cleaner production is not just a response to emerging environmental laws and regulations (Registration, Evaluation, Authorization and Restriction of Chemicals -REACH-, Integrated Pollution Prevention and Control –IPPC- Law, Integrated Product Policy –IPP-), but also a matter of corporate responsibility. Further, it has proved to be a way to increase profits. The sustainability definition has received certain criticism for its vagueness, ambiguity and difficulty to translate this concept at different levels. To overcome the difficulties of its implementation, a wide variety of indicators have been developed and applied over the years, providing metrics essential at the action level. This thesis poses a contribution to the development of environmental evaluation tools adapted to particular production sectors, aiming at providing metrics to guide decision making for the ecodesign of sustainable processes and products. Integrative frameworks that combine methodologies of different nature were proposed as the most suitable way to achieve comprehensive evaluations. At the same time, the simplicity of tools was pursued to make its application easier and more attractive for enterprises, avoiding the need of in depth training

The transition of food consumption towards sustainable patterns based on environmental, economic and nutritional aspects

É máis urxente que nunca acadar un sistema alimentario sostible que sexa respectuoso co medio ambiente, que ofreza seguridade e calidade alimentaria a toda a poboación mundial e, ao mesmo tempo, sexa social e economicamente aceptable. Para iso, os cambios nos patróns alimentarios actuais son unha das ferramentas máis poderosas e eficaces. A adhesión ás dietas tradicionais, baseadas principalmente no consumo de produtos de orixe vexetal e o consumo limitado de produtos de orixe animal e ultra-procesados, considérase como a pedra angular para acadar este obxectivo. Así, esta tese ten como principal finalidade analizar diferentes patróns de consumo de alimentos desde o punto de vista ambiental, nutricional e socioeconómico, e propoñer as medidas axeitadas para lograr patróns dietéticos más sostibles. Ademais, o proceso de produción de alimentos tamén se analiza en profundidade mediante a análise do ciclo de vida de produtos agro-alimentarios relevantes