Open and Closed Loop Inductors for High-Efficiency System-on-Package Integrated Voltage Regulators

Integrated Voltage Regulators (IVR) with integrated magnetics have been shown to provide better efficiency and performance as compared to conventional on-board solutions by reducing power delivery networks (PDN) parasitic, and DC and switching losses. However, IVR integration remains a challenging problem, with a major bottleneck being the integration of power inductors especially for high-efficiency and high-conversion ratio converters in applications such as personal computers and servers, where conversion ratios of 12:1V or 48:1V (with currents of 10A - 200A) are typical. In this paper, package-embedded open and closed loop inductors are designed for a 48:1V 2.5A single-phase converter (basic building block for multi-phase converters to support higher current levels) based on an analysis of the overall system efficiency, considering the simulated characteristics of the inductor dc resistance, ac resistance and inductance, and saturation current. We show that toroidal inductors outperform the solenoidal structures when they are embedded and surrounded by conducting planes, where the former has a higher inductance (32nH vs 16nH) and higher Q-factor (30 vs 21) at 10MHz, and similar DC resistance and saturation current between 5A - 8A.