Adaptive Spread Spectrum Clock Generator using Delta-Sigma Digital-to-Time Converter

修士論

A spread spectrum clock generator based on a short-term optimized chaotic map

4noWe present a spread spectrum clock generator for EMI reduction, where the modulating signal is generated by a suitably designed chaotic map. With respect to past solutions, the map has been designed to achieve a specific short-term behavior of the generated sequences, which allows to optimize the electromagnetic interference peak reduction not only for the theoretical spectrum, but also in the measurement setting prescibed by CISPR norms. In the latter case, we are able to achieve a 3.8dB improvement in EMI reduction with respect to the triangular modulation when using the peak detector, which increases to 6.9 dB when switching to the quasi-peak detector. Results are measured on a prototype which has been designed and fabricated in a 0.18 μm CMOS technology. © 2011 IEEE.partially_openopenPareschi F.; Setti G.; Rovatti R.; Frattini G.Pareschi, F.; Setti, G.; Rovatti, R.; Frattini, G

Increasing the robustness of digital circuits with ring oscillator clocks

Technology scaling enables lower supply voltages, but also increases power density of integrated circuits. In this context, power integrity becomes a major concern in the implementation of highperformance designs. This paper analyzes the influence of Ring Oscillator Clocks (ROCs) on mitigating the impacts of voltage noise. A design with an ROC as the clock source is able to work correctly even in the presence of severe and unpredictable voltage emergencies, without degrading the average performance and power metrics of the circuit. ROCs offer an instantaneous and continuous adaptation to the environment conditions, thus reducing the margins used to prevent timing failures. ROCs provide robustness independently of the power delivery network, thus relaxing the constraints required for the design of the PCB and package. As a by-product, the inherent jitter generated by ROCs produces a spreadspectrum effect that reduces electromagnetic emissions.Peer ReviewedPostprint (published version

Modeling and optimal design of shorting vias to suppress radiated emission in high-speed alternating PCB planes

An analytical mode analysis of vias in the multilayered printed-circuit-board periphery is developed to suppress the electromagnetic radiation induced by ground bounce. After separating the even and odd modes in alternating planes, the far-field radiation of parallel plates is derived using Huygens' principle. It is mainly contributed by the odd mode excitation, while the even mode sets a lower bound on the radiation level from the system when shorting vias are inserted between alternating ground plates. For the odd-mode radiation, a canonical problem is then constructed and analytically solved by applying image theory. Based on that, a systematic approach to achieve the optimum suppression design is developed for the various geometry parameters of the shorting vias, including the pitch, radius, and distance to the board edge. Full-wave simulation and measurement are also presented and the good agreement with the theoretical prediction validates the correctness and efficiency of the present analysis and design

Single-Chip Isolated DC-DC Converter with Self-Tuned Maximum Power Transfer Frequency

abstract: There is an increasing demand for fully integrated point-of-load (POL) isolated DC-DC converters that can provide an isolation barrier between the primary and the secondary side, while delivering a low ripple, low noise regulated voltage at their isolated sides to a high dynamic range, sensitive mixed signal devices, such as sensors, current-shunt-monitors and ADCs. For these applications, smaller system size and integration level is important because the whole system may need to fit to limited space. Traditional methods for providing isolated power are discrete solutions using bulky transformers. Miniaturization of isolated POL regulators is becoming highly desirable for low power applications. A fully integrated, low noise isolated point-of-load DC-DC converter for supply regulation of high dynamic range analog and mixed signal sensor signal-chains is presented. The isolated DC-DC converter utilizes an integrated planar air-core micro-transformer as a coupled resonator and isolation barrier and enables direct connection of low-voltage mixed signal circuits to higher supply rails. The air core transformer is driven at its primary resonant frequency of 100 MHz to achieve maximum power transfer. A mixed-signal perturb-and-observe based frequency search algorithm is developed to improve maximum power transfer efficiency by 60% across the isolation barrier compared to fixed driving frequency method. The isolated converter’s output ripple is reduced by utilizing spread spectrum clocking in the driver. An isolated PMOS LDO in the secondary side is used to suppress switching noise and ripple by 21dB. Conducted and radiated EMI distribution on the IC is measured by a set of integrated ring oscillator based noise sensors with -68dBm noise sensitivity. The proposed isolated converter achieves highest level of integration with respect to earlier reported integrated isolated converters, while providing 50V on-chip junction isolation without the need for extra silicon post-processing steps.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

An absolute calibration system for millimeter-accuracy APOLLO measurements

Lunar laser ranging provides a number of leading experimental tests of gravitation -- important in our quest to unify General Relativity and the Standard Model of physics. The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) has for years achieved median range precision at the ~2 mm level. Yet residuals in model-measurement comparisons are an order-of-magnitude larger, raising the question of whether the ranging data are not nearly as accurate as they are precise, or if the models are incomplete or ill-conditioned. This paper describes a new absolute calibration system (ACS) intended both as a tool for exposing and eliminating sources of systematic error, and also as a means to directly calibrate ranging data in-situ. The system consists of a high-repetition-rate (80 MHz) laser emitting short (< 10 ps) pulses that are locked to a cesium clock. In essence, the ACS delivers photons to the APOLLO detector at exquisitely well-defined time intervals as a "truth" input against which APOLLO's timing performance may be judged and corrected. Preliminary analysis indicates no inaccuracies in APOLLO data beyond the ~3 mm level, suggesting that historical APOLLO data are of high quality and motivating continued work on model capabilities. The ACS provides the means to deliver APOLLO data both accurate and precise below the 2 mm level.Comment: 21 pages, 10 figures, submitted to Classical and Quantum Gravit