A Novel PCB-Embedded Coupled Inductor Structure for a 20-MHz Integrated Voltage Regulator

Abstract

As power demands of processors in portable electronics continuously grow, the voltage regulator (VR) for the processor is expected to be efficient and miniaturized. Compared with a discrete VR solution, the integrated voltage regulator (IVR) can be placed very close to the processor to support dynamic voltage and frequency scaling, which helps significantly reduce the power consumption of the processor. One of the major challenges for IVRs is the high-frequency inductor development. This article proposes a novel, negative-coupled inductor structure with a simple core structure. The coupling coefficient of the proposed structure can be adjusted by changing the inductor winding pattern without modifying the magnetic core structure. The method for adjusting the coupling and the flux distribution in the magnetic core are analyzed in detail. A multiphase integrated inductor is proposed to further enhance the inductor performance by flux cancellation. A printed circuit board (PCB)-embedded four-phase inductor is designed, manufactured, and tested at 20 MHz. The device integrates four inductors into a single-piece magnetic core, featuring an inductance density of 9.7 nH/mm3, a dc resistance (DCR) of 3.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega $ </tex-math></inline-formula> per phase, and a thickness of 0.54 mm with high current-handling ability.