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Very High Frequency IVR for Small Portable Electronics with High-Current Multi-phase 3D Integrated Magnetics

Image of 3D integrated VRM which is assembly of PCB, microprocessor, multi-phase inductor and PMIC
Fig. 1. 3D integrated very high frequency voltage regulator for small portable electronics.
As today's small portable electronics (smartphones, tablets, e-readers, etc.) becomes lighter, thinner, quicker, and smarter, the voltage regulator for the processor is expected to be efficient, miniaturized, integrated, and placed closer to the processor. Power consumption would be reduced dramatically if the supply voltage could be modulated rapidly based on the power demand of each core. However, traditional discrete voltage regulators (VRs) are not able to realize the full potential of DVFS since they are not able to modulate the supply voltage fast enough due to their relatively low switching frequency and the high parasitic interconnect impedance between the VRs and the processors.

Integrated voltage regulators (IVR) with high granularity, small size, near-load integration, and very high switching frequency have been successful in improving the efficiency of power delivery to multi-core processors, such as those implemented in Intel's Haswell and Broadwell processor. This work extends this concept to create the 3D integrated architecture, as shown in Fig. 1 for small portable electronics. The converter is running at tens of MHz to track the core voltage. The multi-phase one-turn inductors are integrated into one magnetic core featuring a simple winding structure, small size, ultra-low profile, ultra-low DCR, high current-handling ability, and air-gap-free magnetics (to effectively confine very high-frequency stray flux). As shown in Figure 2, the five-phase integrated inductor is designed with 0.5 mm in thickness and 16 mm2 in footprint to fit the stringent space requirement of smartphones. The inductor is designed to be stacked with power management IC (PMIC) to save valuable motherboard footprint, and to be placed directly under the processor die to facilitate a short power delivery path. Both single-phase and five-phase integrated inductors are designed, fabricated and experimentally tested at 20 MHz in this work.

Image of multi-phase low profile inductor on planar magnetic core
Fig. 2. Single-phase and multi-phase integrated low profile inductor. The figure shows the self-inductance of each phase and magnetic coupling coefficient between phases at 20 MHz and 3A per phase load condition.
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