Ultra High Frequency Integrated Coupled Inductor Design For IVR in Smartphone Application
As the number of cores in microprocessors and power demands increase in mobile applications, power management is crucial to the whole system. Due to low-frequency operation of voltage regulators in todays smartphone products, passive components occupy lots of space on the motherboard. On the other hand, dynamic voltage and frequency scaling (DVFS) can help reduce power consumption of processors. However, traditional voltage regulators cannot support this function due to low-frequency operation and a long power delivery path. In order to provide a compact and effi- cient power solution for high-performance processors, a three-dimensional integrated voltage regulator (IVR) operating at ultra-high frequency (>10 MHz) is proposed, shown in Fig. 1. The multi-phase inductor is just underneath the processor to shorten the power delivery path. One of the most challenging parts of IVR design is integrated magnetic design with low volume and loss.
In this work, a novel, four-phase integrated coupled inductor structure is proposed, shown in Fig. 2. The structure exploration and design process are illustrated with the help of a finite element tool.
The new inductor structure, operating at 20 MHz switching frequency, features a large current handling ability (15 A peak current) and a very small inductor loss (0.7 W) with a very small footprint (9.6 mm2) and profile (0.3 mm). The inductor sample is fabricated and experimentally tested to verify the design. The thermal performance of the inductor is tested. The inductor is thermal manageable, even operating at 20 MHz due to large surface-area-to-volume ratio of a low-profile inductor structure. Compared with previous inductor design, 70% inductor loss reduction and a 40% footprint and thickness reduction are realized by the new inductor structure.