Trench power MOSFET lowside switch with optimized integrated Schottky diode

Abstract

This work investigates the device and circuit performance of an integrated MOSFET-Schottky diode solution for lowside switching, or synchronous rectifier, applications. The integrated diode structure is a trench MOS barrier Schottky (TMBS) device, and the area of the TMBS structure, as a ratio of the total active area, was the independent variable in this study, ranging from zero to 50%. The results of both simulation and experiments show that there is an optimum contribution of TMBS area which maximizes the performance of the integrated device. Initially, the results provided a strong correlation between TMBS contribution, diode recovery characteristics, and DC-DC converter efficiency. However, a closer examination of the underlying, device level current distribution waveforms, as well as the power loss mechanisms in the converter, reveal a more complex interaction of the TMBS structure and the MOSFET. It is only in the context of this analysis, that useful device design insight can be extracted.