WI - Wireless & RF Magazine: August 2014

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Wi GaN: eGaN FETs for 速

Hard-Switching Converters at High Frequency

The use of gallium nitride (GaN) offers the ability of creating higher performance power switching devices than silicon [1]. Even in its early stages, eGaN FET technology already outperformed the theoretical limits of MOSFETs in the metric of specific on-resistance for a given breakdown voltage [2]. Furthermore, these devices have, from the start, also shown superior figures of merit (FOMs) compared to silicon MOSFETs [3] for both hard- and soft-switching applications. But to improve incircuit efficiency in hard-switching applications requires not only improved device FOMs, but also improvements in printed circuit board layout (PCB) [4] and device package parasitics [5].

In particular, the minimization of both common source inductance (CSI) and power-loop inductance are vital to maximizing the inherent advantage that GaN transistors offer in applications. However, these are not the only important non-GaN device-specific parameters, as will be discussed. In this installment of Wi GaN, we will present hard-switching buck converter results switching at 10 MHz and give a breakdown of the converter losses. We will demonstrate the unmatched high frequency performance capability currently available using eGaN FETs and also highlight the current limitations to pushing to even higher switching frequencies.