Research And Design Of Monolithic Integration Of High-frequency Step-down Dc - Dc Converter

With the development and minimization of portable electronics, it is necessary to design and use high-density system solutions. The continued scaling down of the CMOS process and rapid improvement of integrated-circuits package techniques have made the large off-chip passive components become the bottleneck to constraint the overall system volume. It is now a hot topic in the design of DC-DC converters to reduce the number and size of the off-chip components. Now the switching frequency of the DC-DC converters is increased to reduce the required inductance, but the large off-chip power inductor still dominates the PCB area. It is very attractive to design and realize a fully-integrated DC-DC converter.This thesis begins with the introduction of the basic step-down DC-DC converter, then some control methods and key system specifications. Based on the requirement of low-frequency DC-DC converters, on-chip passive components for high-frequency DC-DC converters are properly designed in the target CMOS process. The on-chip inductor has asymmetric structure to improve the quality factor and, thereby, the power conversion efficiency. High-density capacitor structure is designed to smooth the output voltage and reduce the output ripple. According to the characteristic of the control loop, simple voltage control mode and basic PI compensation are employed to ensure the stability of the converter. The prototype converter was fabricated in SMIC 0.13μm 1.2V/3.3V CMOS process. Measurement results demonstrate the feasibility of fully-integrated DC-DC converter with the switching frequency up to 250MHz. The peak efficiency is 70%, when the input voltage is 3.3V and the output voltage is 1.8V. The maximum output current is 400mA. The output ripple is smaller than 5 percent. The load response time is smaller than 100ns.