A 7.3-μ W 13-ENOB 98-dB SFDR Noise-Shaping SAR ADC With Duty-Cycled Amplifier and Mismatch Error Shaping

This article presents a second-order noise-shaping successive-approximation-register (SAR) analog-to-digital converter (ADC) that employs a duty-cycled amplifier and digital-predicted mismatch error shaping (MES). The loop filter is composed of an active amplifier and two cascaded passive integrators to provide a theoretical 30-dB in-band noise attenuation. The amplifier achieves 18\times gain in a power-efficient way thanks to its inverter-based topology and duty-cycled operation. The capacitor mismatch in the digital-to-analog converter (DAC) array is mitigated by first-order MES. A two-level digital prediction scheme is adopted with MES to avoid input range loss. Fabricated in 65-nm CMOS technology, the prototype achieves 80-dB peak signal-to-noise-and-distortion-ratio (SNDR) and 98-dB peak spurious-free-dynamic-range (SFDR) in a 31.25-kHz bandwidth with 16\times oversampling ratio (OSR), leading to a Schreier figure-of-merit (FoM) of 176.3 dB and a Walden FoM of 14.3 fJ/conversion-step.</p

Low power CMOS IC, biosensor and wireless power transfer techniques for wireless sensor network application

The emerging field of wireless sensor network (WSN) is receiving great attention due to the interest in healthcare. Traditional battery-powered devices suffer from large size, weight and secondary replacement surgery after the battery life-time which is often not desired, especially for an implantable application. Thus an energy harvesting method needs to be investigated. In addition to energy harvesting, the sensor network needs to be low power to extend the wireless power transfer distance and meet the regulation on RF power exposed to human tissue (specific absorption ratio). Also, miniature sensor integration is another challenge since most of the commercial sensors have rigid form or have a bulky size. The objective of this thesis is to provide solutions to the aforementioned challenges

Electrochemical Plug-and-Power e-readers for Point-of-Care Applications

Point-of-Care diagnostic tests enable monitor health conditions and obtain fast results close to the patient, reducing medical costs, and allowing the control of infectious outbreaks. The interest in developing Point-of-Care devices is increasing due to they are suitable for a wide variety of applications. This doctoral thesis focuses on the development of Plug-and-Power electronic readers (e- readers) for electrochemical detections and the demonstration of their possibilities as Point-of-Care diagnostic testing. The solutions proposed in this study make it possible to improve Point-of-Care tests whose premises are laboratory decentralization, personalized medicine, rapid diagnosis, and improvement of patient care. Developed electronic readers can be powered from a conventional system, such as a USB port or a lithium battery, or can be defined as self-powered systems, capable of extracting energy from alternative energy sources, such as fuel cells, defining Plug-and-Power systems. The designed electrochemical detection devices in this thesis are based on low-power consumption electronic instrumentation circuits. These circuits are capable of controlling the sensing element, measuring its response, and representing the result quantitatively. The implemented devices can work with both electrochemical sensors and fuel cells. Furthermore, it is possible to adapt its measurement range, enabling its use in a wide variety of applications. Thanks to their reduced energy consumption, some of these developments can be defined as self-powered platforms able to operate only with the energy extracted from the biological sample, which in turn is monitored. These devices are easy-to-use and plug-and-play, enabling those unskilled individuals to carry out tests after prior training. Moreover, thanks to their user-friendly interface, results are clear and easy to understand. This doctoral dissertation is presented as an article compendium and composed of three publications detailed in chronological order of publication. The first contribution describes an innovative portable Point-of-Care device able to provide a quantitative result of the glucose concentration of a sample. The proposed system combines an e-reader and a disposable device based on two elements: a glucose paper-based power source, and a glucose fuel cell-based sensor. The battery-less e-reader extracts the energy from the disposable unit, acquires the signal, processes it, and shows the glucose concentration on a numerical display. Due to low-power consumption of the e-reader, the whole electronic system can operate only with the energy extracted from the disposable element. Furthermore, the proposed system minimizes the user interaction, which only must deposit the sample on the strip and wait a few seconds to see the test result. The second publication validates the e-reader in other scenarios following two approaches: using fuel cells as a power element, and as a dual powering and sensing element. The device was tested with glucose, urine, methanol, and ethanol fuel cells and electrochemical sensors in order to show the adaptability of this versatile concept to a wide variety of fields beyond clinical diagnostics, such as veterinary or environmental fields. The third study presents a low-cost, miniaturized, and customizable electronic reader for amperometric detections. The USB-powered portable device is composed of a full- custom electronic board for signal acquisition, and software, which controls the systems, represents and saves the results. In this study, the performance of the device was compared against three commercial potentiostats, showing comparable results to those obtained using three commercial systems, which were significantly more expensive. As proof of concept, the system was validated by detecting horseradish peroxidase samples. However, it could be easily extended its scope and measure other types of analytes or biological matrices since it can be easily adapted to detect currents a wide range of currents.Las pruebas de diagnostico Point-of-Care permiten monitorizar las condiciones de salud y obtener resultados rápidos cerca del paciente, reduciendo los costes médicos y permitiendo controlar brotes infecciosos. El interés por desarrollar dispositivos de Point- of-Care está aumentando debido a que son aplicables a una amplia variedad de aplicaciones. Esta tesis doctoral se centra en el desarrollo de lectores electrónicos (e-readers) Plug-and- Power para detecciones electroquímicas y la demostración de sus posibilidades como pruebas de diagnóstico de punto de atención (Point-of-Care). Las soluciones propuestas en este trabajo permiten mejorar las pruebas Point-of-Care, cuyas premisas son la descentralización de laboratorio, la medicina personalizada, el diagnóstico rápido y la mejora de la atención al paciente. Los lectores electrónicos desarrollados pueden ser alimentados desde un sistema convencional, como puede ser un puerto USB o una batería de litio, o definirse como sistemas autoalimentados, capaces de extraen energía de fuentes alternativas de energía, como celdas de combustible (fuel cells), definiendo así sistemas Plug-and-Power. Los dispositivos de detección electroquímica diseñados se basan en circuitos de instrumentación electrónica de bajo consumo. Estos circuitos son capaces controlar el elemento de sensado, medir su respuesta y representar el resultado de forma cuantitativa. Los dispositivos implementados pueden trabajar tanto con sensores electroquímicos como con fuel cells. Además, es posible adaptar su rango de medida, permitiendo su utilización en una amplia variedad de aplicaciones. Gracias a su reducido consumo de energía, algunos de estos desarrollos pueden definirse como plataformas autoalimentadas capaces de operar solo con la energía extraída de la muestra biológica, que a su vez es monitorizada. Estas plataformas electrónicas son fáciles de usar y Plug-and-Play, permitiendo que personas no cualificadas puedan utilizarlas después de un previo entrenamiento. Además, gracias a su interfaz fácil de usar, los resultados son claros y fáciles de interpretar

Low-Voltage, Low-Area, nW-Power CMOS Digital-Based Biosignal Amplifier

This paper presents the operation principle and the silicon characterization of a power efficient ultra-low voltage and ultra-low area fully-differential, digital-based Operational Transconductance Amplifier (OTA), suitable for microscale biosensing applications (BioDIGOTA). Measured results in 180nm CMOS prototypes show that the proposed BioDIGOTA is able to work with a supply voltage down to 400 mV, consuming only 95 nW. Owing to its intrinsically highly-digital feature, the BioDIGOTA layout occupies only 0.022 mm2 of total silicon area, lowering the area by 3.22X times compared to the current state of the art, while keeping reasonable system performance, such as 7.6 NEF with 1.25 μVRMS input referred noise over a 10 Hz bandwidth, 1.8% of THD, 62 dB of CMRR and 55 dB of PSRR

Low-voltage, low-area, nW-power CMOS digital-based biosignal amplifier

This paper presents the operation principle and the silicon characterization of a power efficient ultra-low voltage and ultra-low area fully-differential, digital-based Operational Transconductance Amplifier (OTA), suitable for microscale biosensing applications (BioDIGOTA). Measured results in 180nm CMOS prototypes show that the proposed BioDIGOTA is able to work with a supply voltage down to 400 mV, consuming only 95 nW. Owing to its intrinsically highly-digital feature, the BioDIGOTA layout occupies only 0.022 mm2 of total silicon area, lowering the area by 3.22× times compared to the current state of the art, while keeping reasonable system performance, such as 7.6 NEF with 1.25 μVRMS input referred noise over a 10 Hz bandwidth, 1.8% of THD, 62 dB of CMRR and 55 dB of PSRR

Integrated Circuits for Medical Ultrasound Applications: Imaging and Beyond

Medical ultrasound has become a crucial part of modern society and continues to play a vital role in the diagnosis and treatment of illnesses. Over the past decades, the develop- ment of medical ultrasound has seen extraordinary progress as a result of the tremendous research advances in microelectronics, transducer technology and signal processing algorithms. How- ever, medical ultrasound still faces many challenges including power-efficient driving of transducers, low-noise recording of ultrasound echoes, effective beamforming in a non-linear, high- attenuation medium (human tissues) and reduced overall form factor. This paper provides a comprehensive review of the design of integrated circuits for medical ultrasound applications. The most important and ubiquitous modules in a medical ultrasound system are addressed, i) transducer driving circuit, ii) low- noise amplifier, iii) beamforming circuit and iv) analog-digital converter. Within each ultrasound module, some representative research highlights are described followed by a comparison of the state-of-the-art. This paper concludes with a discussion and recommendations for future research directions

Integrated Circuit Design for Miniaturized, Trackable, Ultrasound Based Biomedical Implants

This thesis focuses on the design of an ultrasonography compatible implantable sensor platform, as a novel approach that implements a miniaturized, battery-less, real-time trackable parallel biosensing system. In addition to the frontend circuit, a sub-nW fully integrated pH sensor is designed in a way that can be easily integrated with the proposed sonography-compatible sensor platform. Combining the two integrated circuits together, the whole system will be able to map in vivo physiological information acquired from a distributed set of sensors on top of the ultrasound movie, leading to the idea envisioned as “augmented ultrasonography”. Implemented in a 0.18 μm technology, an ultrasound power and data frontend circuit is designed to enable medical sensing implants to operate in an ultrasonography compatible way. When placed within the field of view of an imaging transducer, the frontend circuit harvests the power through a piece of piezo crystal from a minimally modified brightness-mode (B-mode) ultrasound imaging process that is commonly adopted in modern medical practices. The implant can also establish bi-directional data communication channels with the imaging transducer, allowing data to be transmitted in a way synchronized to the frame rate of the B-mode film. The design of the circuit is made possible by a combination of ultra-low-power circuit techniques and novel frontend circuit topologies, as imaging ultrasound waves in the form of short pulses with extremely low duty cycle poses challenges that has not previously seen in other implantable sensor systems. The proposed prototype achieves a total area of 0.6mm² for the integrated circuit (IC), as well as 71mm theoretical maximum implantable depth (up to 40 mm is verified experimentally). These two together give opportunities for this design to become the next generation solution for deep-tissue bio-sensing implants. Realized using the same 0.18 μm technology, the fully integrated pH sensor is designed to deliver accurate pH readouts, at a reasonable speed of 1 sample per second, while consuming only 0.72 nW of power. Using an ion-sensitive field effect transistor (ISFET) and reference field effect transistor pair (REFET), the IC requires minimum additional post fabrication to deliver 10-bit resolution pH readouts at an end-to-end sensitivity of 65.8 LSB/pH. When working as a standalone device, this work advances the state-of-the-art of ISFET based pH sensor design. With an addition of 0.46 mm² of area, it is possible to integrate it with the ultrasound sonography compatible implant platform. This potential integration will further advance the vision of the augmented ultrasonography: real-time display of physiological information in a B-mode film, with the help from a distributed bio-sensor system for deep-tissue physiology monitoring

DESIGN OF LOW-POWER LOW-VOLTAGE SUCCESSIVE-APPROXIMATION ANALOG-TO-DIGITAL CONVERTERS

Ph.DDOCTOR OF PHILOSOPH

CMOS MULTI-MODAL INTEGRATED SYSTEMS FOR FUTURE BIOELECTRONICS AND BIOSENSORS

Cells are the basic structural biological units of all known living organisms. They are highly sophisticated system with thousands of molecules operating in hundreds of pathways to maintain their proper functions, phenotypes, and physiological behaviors. With this scale of complexity, cells often exhibit multi-physiological properties as their cellular fingerprints from external stimulations. In order to further advance the frontiers in bioscience and biotechnologies such as stem cell manufacturing, synthetic biology, and regenerative medicine, it is required to comprehend complex cell physiology of living cells. Therefore, a comprehensive set of technologies is needed to harvest quantitative biological data from given cell samples. Such demands have stimulated extensive research on new bioelectronics and biosensors to characterize their functional information by converting their biological activities to electrical signals. As a result, various bioelectronics and biosensors are reported and employed in many in vivo and in vitro applications. Since sensing electrodes of the devices are physically in touch with biological/chemical samples and record their signals, long-term biocompatibility and chemical/mechanical stability is of paramount importance in numerous biological applications. Furthermore, the devices should achieve high sensitivity/resolution/linearity, large field-of-view (FoV), multi-modal sensing, and real-time monitoring, while maintaining small feature size of devices to use small volume of biological/chemical samples and reduce cost. As a result, My Ph.D research aims to study interfacial electrochemical impedance spectroscopy (EIS) of electrodes with different combination of materials/sizes and to design novel multi-modal sensing/actuation array architectures with CMOS compatible in-house post-processing to address the design challenges of the bioelectronics and biosensors.Ph.D

Dopamiinin hapettumisen lukija-anturirajapinta 65 nm CMOS teknologialla

Sensing and monitoring of neural activities within the central nervous system has become a fast-growing area of research due to the need to understand more about how neurons communicate. Several neurological disorders such as Parkinson’s disease, Schizophrenia, Alzeihmers and Epilepsy have been reported to be associated with imbalance in the concentration of neurotransmitters such as glutamate and dopamine [1] - [5]. Hence, this thesis proposes a solution for the measurement of dopamine concentration in the brain during neural communication. The proposed design of the dopamine oxidation readout sensor interface is based on a mixed-signal front-end architecture for minimizing noise and high resolution of detected current signals. The analog front-end is designed for acquisition and amplification of current signals resulting from oxidation and reduction at the biosensor electrodes in the brain. The digital signal processing (DSP) block is used for discretization of detected dopamine oxidation and reduction current signals that can be further processed by an external system. The results from the simulation of the proposed design show that the readout circuit has a current resolution of 100 pA and can detect minimum dopamine concentration of 10 μMol based on measured data from novel diamond-like carbon electrodes [6]. Higher dopamine concentration can be detected from the sensor interface due to its support for a wide current range of 1.2 μA(±600 nA). The digital code representation of the detected dopamine has a resolution of 14.3-bits with RMS conversion error of 0.18 LSB which results in an SNR of 88 dB at full current range input. However, the attained ENOB is 8-bits due to the effect of nonlinearity in the oscillator based ADC. Nonetheless, the achieved resolution of the readout circuit provides good sensitivity of released dopamine in the brain which is useful for further understanding of neurotransmitters and fostering research into improved treatments of related neurodegenerative diseases.Keskushermoston aktiivisuuden havainnointi ja tarkkailu on muodostunut tärkeäksi tutkimusalaksi, sillä tarve ymmärtää neuronien viestintää on kasvanut. Monien hermostollisten sairauksien kuten Parkinsonin taudin, skitsofrenian, Alzheimerin taudin ja epilepsian on huomattu aiheuttavan muutoksia välittäjäaineiden, kuten glutamaatin ja dopamiinin, pitoisuuksissa [1] - [5]. Aiheeseen liittyen tässä työssä esitetään ratkaisu dopamiinipitoisuuden mittaamiseksi aivoista. Esitetty dopamiinipitoisuuden lukijapiiri perustuu sekamuotoiseen etupäärakenteeseen, jolla saavutetaan matala kohinataso ja hyvä tarkkuus signaalien ilmaisemisessa. Suunniteltu analoginen etupää kykenee lukemaan ja vahvistamaan dopamiinipitoisuuden muutosten aiheuttamia virran muutoksia aivoihin asennetuista elektrodeista. Digitaalisen signaalinkäsittelyn avulla voidaan havaita dopamiinin hapettumis-ja pelkistymisvirtasignaalit, ja välittää ne edelleen ulkoisen järjestelmän muokattavaksi. Simulaatiotulokset osoittavat, että suunniteltu piiri saavuttaa 100 pA virran erottelukyvyn. Simuloinnin perustuessa hiilipohjaisiin dopamiinielektrodeihin piiri voi havaita 10 μMol dopamiinipitoisuuden [6]. Myös suurempia dopamiinipitoisuuksia voidaan havaita, sillä etupäärajapinta tukee 1.2 μA(±600 nA) virta-aluetta. Digitaalinen esitysmuoto tukee 14.3 bitin esitystarkkuutta 0.18 bitin RMS virheellä saavuttaen 88 dB dynaamisen virta-alueen. Saavutettu ENOB (tehollinen bittimäärä) on kuitenkin 8 bittiä oskillaattoripohjaisen ADC:n (analogia-digitaalimuuntimen) epälineaarisuuden takia. Saavutettu tarkkuus tuottaa hyvän herkkyyden dopamiinin havaitsemiseksi ja hyödyttää siten välittäjäainetutkimusta ja uusien hoitomuotojen kehittämistä hermostollisiin sairauksiin