This book discusses in detail the fundamental principles and design specifications governing fully-integrated temperature sensors in deep-submicron CMOS technology. It provides an in-depth analysis of diverse sensing and readout circuit architectures, cutting-edge ultra-low-voltage and frequency-locked loop (FLL) design methodologies, and detailed implementation strategies. Readers will gain valuable insights from the latest advancements in deep-submicron CMOS technology, mastering a range of precision-driven, area- and energy-efficient techniques. This knowledge empowers readers to identify and develop optimal architectures tailored to specific applications and technology nodes. Moreover, the book serves as an invaluable resource for professionals in circuit and system design, particularly those focused on temperature sensing systems or high-performance integrated circuits, offering practical guidance for researchers and engineers in both academia and industry.