Instituto de Microelectrónica de Sevilla (IMSE-CNM)
URI permanente para esta colecciónhttps://hdl.handle.net/11441/11499
Examinar
Envíos recientes
Tesis Doctoral Diseño de circuitos integrados para interfaces neuronales implantables(2020-06-10) Valtierra, José Luis; Delgado Restituto, Manuel ; Rodríguez Vázquez, Ángel Benito; Universidad de Sevilla. Departamento de Electrónica y ElectromagnetismoProgress in microfabrication technology has opened the way for new possibilities in neuroscience and medicine. Chronic, biocompatible brain implants with recording and stimulation capabilities provided by embedded electronics have been successfully demonstrated. However, more ambitious applications call for improvements in every aspect of existing implementations. This thesis proposes two prototypes that advance the field in significant ways. The first prototype is a neural recording front-end with spectral selectivity capabilities that implements a design strategy that leads to the lowest reported power consumption as compared to the state of the art. The second one is a bidirectional front-end for closed-loop neuromodulation that accounts for self-interference and impedance mismatch thus enabling simultaneous recording and stimulation. The design process and experimental verification of both prototypes is presented herein.Tesis Doctoral Design of CMOS Digital Silicon Photomultipliers with ToF for Positron Emission Tomography(2020-05-29) Bandi, Franco Nahuel; Carmona Galán, Ricardo; Rodríguez Vázquez, Ángel Benito; Universidad de Sevilla. Departamento de Electrónica y ElectromagnetismoThis thesis presents a contribution to the design of single-photon detectors for medical imaging. Specifically, the focus has been on the development of a pixel capable of single-photon counting in CMOS technology, and the associated sensor thereof. These sensors can work under low light conditions and provide timing information to determine the time-stamp of the incoming photons. For instance, this is particularly attractive for applications that rely either on time-of-flight measurements or on exponential decay determination of the light source, like positron emission tomography or fluorescence-lifetime imaging, respectively. This thesis proposes the study of the pixel architecture to optimize its performance in terms of sensitivity, linearity and signal to noise ratio. The design of the pixel has followed a bottom-up approach, taking care of the smallest building block and studying how the different architecture choices affect performance. Among the various building blocks needed, special emphasis has been placed on the following: • the Single-Photon Avalanche Diode (SPAD), a photodiode able to detect photons one by one; • the front-end circuitry of this diode, commonly called quenching and recharge circuit; • the Time-to-Digital Converter (TDC), which determines the timing performance of the pixel. The proposed architectural exploration provides a comprehensive insight into the design space of the pixel, allowing to determine the optimum design points in terms of sensor sensitivity, linearity or signal to noise ratio, thus helping designers to navigate through non-straightforward trade-offs. The proposed TDC is based on a voltage-controlled ring oscillator, since this architecture provides moderate time resolutions while keeping the footprint, the power, and conversion time relatively small. Two pseudo-differential delay stages have been studied, one with cross-coupled PMOS transistors and the other with cross-coupled inverters. Analytical studies and simulations have shown that cross-coupled inverters are the most appropriate to implement the TDC because they achieve better time resolution with smaller energy per conversion than cross-coupled PMOS transistor stages. A 1.3×1.3 mm2 pixel has been implemented in an 110 nm CMOS image sensor technology, to have the benefits of sub-micron technologies along with the cleanliness of CMOS image sensor technologies. The fabricated chips have been used to characterize the single-photon avalanche diodes. The results agree with expectations: a maximum photon detection probability of 46 % and a median dark count rate of 0.4 Hz/µm2 with an excess voltage of 3 V. Furthermore, the characterization of the TDC shows that the time resolution is below 100 ps, which agrees with post-layout simulations. The differential non-linearity is ±0.4LSB, and the integral non-linearity is ±6.1LSB. Photoemission occurs during characterization - an indication that the avalanches are not quenched properly. The cause of this has been identified to be in the design of the SPAD and the quenching circuit. SPADs are sensitive devices which maximum reverse current must be well defined and limited by the quenching circuit, otherwise unwanted effects like excessive cross-talk, noise, and power consumption may happen. Although this issue limits the operation of the implemented pixel, the information obtained during the characterization will help to avoid mistakes in future implementations.Artículo Dynamic simulation of the temperature inlet turbine control system for an unfired micro gas turbine in a concentrating solar tower(Elsevier, 2018-08) Amelio, Mario; Silva Pérez, Manuel Antonio; Ferraro, Vittorio; Rovense, Francesco; Bova, Sergio; Universidad de Sevilla. Departamento de Ingeniería EnergéticaIn this work, the dynamic performance of a mass flow regulation system, in a concentrating solar tower plant, with unfired closed micro gas turbine, during clouds transient will be presented. The adjustment system operates with the heliostats field control system, in order to control the temperature inlet turbine. To choose the best configuration, the performance of three heliostats sizes, for four Solar Multiple, has been evaluated. The design of the solar field was carried out by means of Solar Pilot, while the numerical models have been developed in Matlab/Simulink. The results show that a particular configuration is suitable for this purpose.