An Ultra-Low-Quiescent-Current Dual-Mode Digitally-Controlled Buck Converter IC for Cellular Phone Applications

This dissertation presents a low-quiescent-current dual-mode digitally-controlled buck converter IC for cellular phone applications. In cellular phones, the load current demanded by the on-board circuitry varies from below 0.1 mA up to a few hundred mA, reflecting operation in standby and active (talk) modes. Thus, high efficiency over a wide load range is of high priority for power management units, since the total energy is limited by the capacity of a single cell Li-ion battery. A dual-mode buck converter IC, implemented with a 0.25-µm CMOS process, takes 2 mm 2 active area and demonstrates equal or better regulation performance compared to state-of-the-art analog switchers. A very low quiescent current of 4 µA is achieved experimentally, resulting in a more than threefold reduction compared to 2 the leading state-of-the-art analog controllers. Consequently, a high efficiency, exceeding 70%, is achieved over a wide load range between 0.1 and 400 mA. iii To my parents, your love means the whole world to me. iv Acknowledgements First of all, I would like to express my gratitude to Professor Seth Sanders, for his patient guidance through my five years of graduate school life, for his unconditional support to my work, for his uncountable help in technical writing, and for being a wonderful role model. He is the most intelligent and unselfish person I have ever known, and I truly feel very fortunate to have had the opportunity to be his student. Nikolic, and Paul Wright for serving on my qualifying exam committee. I would also like to thank Professors Sanders, Niknejad, and Wright for reading this thesis. I would also like to thank my colleagues in Professor Sanders' group for their friendship and help over the years. Perry Tsao helped me many times on computer related problems with great patience. Angel Peterchev provided not only countless valuable technical discussions and ideas, but also shared his insight into art, and his talent for painting. Jianhui Zhang and his wife Rui Chen were a great couple to discuss any issue with. Artin Der Minassians, Matthew Senesky, Gabriel Eirea, and Wei Wang made 341 Cory Hall a fun place to work. I greatly value the friendship and support from two other residents in 341 Cory Hall, Lixia Zhou and Jin Wang. Lixia always encouraged me when I was feeling down. She was also a very competitive company in swimming. Jin Wang helped me with valuable discussions in the …