Analysis and Design of On-Chip Magnetic Core Solenoid Inductors for Integrated Power Converters

The miniaturization of power electronics is an ever-ongoing challenge with the goal of increasing overall system efficiency and decreasing volume. The high-density integration of passive components, such as inductors and transformers, proves to be a crucial factor in advancing power supply on chip (PwrSoC) performance. In radio-frequency integrated circuits (RFIC) integrated inductors are indispensable, while for PwrSoC the high inductance to DC resistance ratio (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L/R_DC</i>) requirements have limited their usage. On-chip magnetic core inductors aim to overcome this limitation. To provide guidance in the design of integrated magnetic thin-film solenoid inductors, a comprehensive analysis of the design space in a state-of-the-art commercially available technology is performed in this paper. While much has been reported on individual designs and technologies, a design space evaluation including trade-offs and design considerations has not been presented for solenoid thin-film inductors yet. Quality factor enhancing techniques are addressed, as well as the optimal switching frequency for power applications. It is complemented by an electromagnetic (EM) field simulation based design and optimization approach and addresses the difficulties of accurate circuit model representations for transient simulations. The EM simulation models are carefully verified by measurements up to 1 GHz.