High Inductance Density Low-Profile Inductor Structure for Integrated Point-of-Load Converter

This paper presents a 3D integrated solution that uses a low-profile planar inductor as the substrate as one of the possible methods to integrate the magnetic component with the active component. In order to reduce the inductor size to achieve a more compact integrated converter, several low-profile inductor structures with different flux path patterns (vertical or lateral) based on low temperature co-fired ceramics (LTCC) technology are studied and compared. Some lateral flux structures are proposed to increase the inductance density for a low-profile inductor design. A 1.5 MHz, 5 V to 1.2 V, 3D integrated buck converter with LTCC inductor substrate is designed and fabricated and Compared with a vertical flux structure, the proposed lateral flux structure can help to save around 30% of the footprint. The full load (Io= 15 A) efficiency of this 3D integrated buck converter is around 87%. The power density of this integrated converter is as high as 300 W/in³.