Fully Integrated Voltage Regulators (FIVRs) with Package In-situ Coupled CoaxMIL Inductor for High Power Density Microprocessor Applications

CoaxMIL inductors are the latest package in-situ inductors with a high ratio of inductance to resistance for fully integrated voltage regulators (FIVRs). However, it is challenging to achieve both high efficiency and high density with CoaxMIL due to the fundamental performance trade-off of uncoupled inductors. This paper introduces a coupled package integrated coaxial magnetic inductor (CoaxMIL-C), which relieves the trade-off of CoaxMIL. By adding phase coupling to CoaxMIL structures, the proposed CoaxMIL-C reduces the inductor size by 33% and improves the transient performance while maintaining the efficiency of conventional CoaxMIL inductors. Performance is verified with lab measurements and validated with a FIVR test bench with external inductor pads. CoaxMIL-C provides 24 A/mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> maximum density and enables the FIVR to achieve 89% peak efficiency at 1.75 V to 0.75 V conversion.