On-Chip Timing Control

Abstract

Oscillators represent an essential building block for many electronic, communication, and optical systems. They are used in digital electronic systems to provide them with the reference clock signal required for synchronizing their operation. Thus, oscillators must work with high accuracy and temperature stability in order not to a ect the cor- rect operation of these applications. However, di erent variations like supply, process, and temperature variations greatly a ect the output frequency of oscillators. Supply and process variations can be calibrated at the beginning of the oscillator operation. Temperature variations represent the bottleneck for improving the oscillator stability. Therefore, many oscillators are developed over years to enhance their temperature sta- bility. Some of them can achieve very low temperature variations like crystal oscillators; however, they are not suitable for full integration and have large area and cost. Thus, this thesis focuses on the design of a new frequency control loop that adjusts the output frequency of an oscillator regardless of its temperature variations. A new tech- nique that utilizes a switched-capacitor circuit is proposed for controlling the oscillator frequency. Also, a bandgap reference circuit is used to adjust the oscillator frequency to the desired value so that there is no need for an external reference oscillator. The proposed switched-capacitor-based frequency control loop can achieve very high tem- perature stability with low power. Also, it is suitable for on-chip integration. The thesis is divided into six chapters as listed below: Chapter 1 It is an introduction to the proposed work including the motivations, objective, and main contributions of this thesis. Chapter 2 It gives an overview of the di erent types of oscillators, focusing on the advantages and disadvantage of each type and making a brief comparison between them. Also, it presents the factors that a ect the output frequency of an oscillator. Chapter 3 In chapter 3, the proposed switched-capacitor-based frequency control loop is presented. The principle of its operation along with its building blocks are introduced. System x modeling is developed to analyze the system performance. In addition, the concepts of composite-resistor temperature compensation and oven-controlled components are introduced. Chapter 4 It deals with the circuit implementation of the di erent building blocks of the pro-