8.1 Overview

LMG341xR050 is a high-performance 600-V GaN transistor with integrated gate driver. The GaN transistor provides ultra-low input and output capacitance and zero reverse recovery charge. The lack of reverse recovery charge enables efficient operation in half-bridge and bridge-based topologies.

TI utilizes a Direct Drive architecture to control the GaN FET within the LMG341xR050. When the driver is powered up, the GaN FET is controlled directly with the integrated gate driver. This architecture provides superior switching performance compared with the traditional cascode approach for switching depletion mode FET.

The integrated driver solves a number of challenges using GaN devices. The LMG341xR050 contains a driver specifically tuned to the GaN device for fast driving without ringing on the gate. The driver ensures the device stays off for high drain slew rates up to 150 V/ns. In addition, the integrated driver protects against faults by providing overcurrent and overtemperature protection. This feature can protect the system in case of a device failure, or prevent a device failure in the case of a controller error or malfunction. LMG3410R050 and LMG3411R050 have the same design and features, except the handling of OCP events. LMG3410R050 adopts a latch-off strategy at OCP events, while LMG3411R050 can realize cycle-by-cycle current limit function. Please refer to Fault Detection for more details.

Unlike silicon MOSFETs, there is no p-n junction from source to drain in GaN devices. That is why GaN devices have no reverse recovery losses. However, the GaN device can still conduct from source to drain in third-quadrant of operation similar to a body diode but with higher voltage drop and higher conduction loss. Third-quadrant operation can be defined as follows; when the GaN device is turned off and negative current pulls the drain node voltage to be lower than its source. The voltage drop across GaN device during third-quadrant operation is high; therefore, it is recommended to operate with synchronous switching and keep the duration of third-quadrant operation at minimum.