Low profile LTCC inductor substrate for multi-MHz integrated POL converter

The emerging Gallium Nitride (GaN) based power device enables high frequency point-of-load (POL) converter with high current capability. This paper presents the low profile LTCC inductor substrate design and evaluation for multi-MHz 3D integrated POL module with GaN device. In the design process, the core thickness and loss of the inductor are main considerations. The impact of different frequency on the LTCC inductor substrate design is discussed. The LTCC inductors and some commercial discrete inductors are experimentally evaluated on a 12V to 1.2V 15A POL converter built with EPC´s GaN devices. The comparison demonstrates that the LTCC inductor can dramatically improve the converter light load efficiency due to its nonlinear inductance, while maintain almost the same full load efficiency as the discrete inductor. Because of the low profile design, the power density of the POL module with LTCC inductor is much higher than that with discrete inductor. The 3D integrated POL module achieves 84.5% efficiency and 700W/in³ power density at 2MHz, 81.8% efficiency and 800W/in³ power density at 3MHz.