Design of an Ultra Low Power SIMO Boost Converter for Audio Applications

This thesis presents an ultra low power Single Inductor Multiple Output (SIMO) boost converter tailored for audio applications, specifically for wireless earbuds. In the audio device market, where the goal is to achieve increasingly higher performance while minimizing power consumption, power management systems play a fundamental role by ensuring efficient energy management, optimizing battery life and allowing the Power Amplifier (PA) to deliver consistent audio quality across different operating conditions. This converter is integrated into a larger system aimed at driving a piezoelectric Micro-Electro-Mechanical System (MEMS) speaker through a Class-AB PA, which supports both analog and digital inputs. The thesis begins with the description of the driving methods for MEMS speakers, followed by basic concepts related to the boost converter, which can also be applied to other DC-DC converters topologies. Finally, the general structure and the description of the entire chip, named IVM6311, is provided, with a focus on the design and optimization of the SIMO Boost Converter, supported by simulation and measurement results. The whole chip is implemented using a 180nm BCD process in a total area of 4.2mm² and the power consumption achieved by the boost converter in a typical case, like 20Vpp on the MEMS speaker, is lower than 4mW.