26 AC/DC DC/DC https://www.analog.com/ Issue 3 2025 Power Electronics Europe www.power-mag.com Can You Drive GaNFETs with a DC-to-DC Controller Originally Designed for Silicon MOSFETs? Kevin Thai, Applications Manager, Analog Devices Question How can I design a 4-switch buck-boost DC-to-DC converter using GaNFETs when there are no controllers specifically made to drive GaNFETs available? choosing the correct drive voltage and some small protection circuitry can provide a safe, all-in-one, high frequency GaN drive for a 4-switch buck-boost controller. Introduction In the never-ending quest to reduce board size and increase efficiency, gallium nitride field effect transistor (GaNFET) power devices have become an ideal candidate Answer GaNFETs are notoriously more difficult to drive and may require extra protection components if using a driver meant for silicon (Si) MOSFETs. Proper care in to push these boundaries. GaN is an emerging technology that promises higher power with ultrafast switching and reduced switching losses. These advantages allow for more power dense solutions. The current market is saturated with a myriad of different Si MOSFET drivers, and new GaN drivers and controllers with built-in GaN drivers are some years away from becoming accessible. Along with simple, dedicated GaNFET drivers (such as the LT8418), complex buck and boost controllers targeted for GaN exist on the market (LTC7890, LTC7891). There is still no straightforward 4-switch buck-boost solution. However, driving GaNFETs is not as difficult as it may seem. With some simple background knowledge, Si MOSFET targeted controllers can be adapted to drive GaNFETs. The LT8390A is a great candidate as it is a unique 2MHz buckboost controller with very low dead time (25ns) (see Figure 1). The buck-boost scheme has the sense resistor in line with the inductor and outside of both hot loops - a novel feature for buck-boosts. This allows the controller to operate in peak Figure 1. EVAL-LT8390A-AZ 24VOUT 5A 4-switch buck-boost GaN controller schematic.
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