Fan-Out-Package-Embedded Coupled Inductors for Integrated Voltage Conversion

In this paper, novel fan-out-package-embedded coupled inductors are proposed and demonstrated for integrated voltage conversion. The coupled inductors have two interleaved thick windings embedded in a silicon-based fan-out package and surrounding an embedded die which is the control IC of a voltage converter. Fan-out-package-embedded coupled inductors with an inductance of 2.5 nH and a coupling factor of 0.85 are designed and fabricated for a high-frequency buck converter application. The fabricated coupled inductors show a dc resistance of 5 mΩ and an ac resistance of 77 mΩ at 170 MHz. Using the coupled inductors, the integrated converter achieves a very high efficiency of 90.4% for 0.19 A, 170 MHz, 1. 2–0.9V voltage conversion, which is significantly higher than that of the converters implemented using other inductor approaches.