8.1 Overview

LMG341xR070 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. The lack of reverse recovery enables efficient operation in half-bridge and bridge-based topologies.

TI utilizes a Direct Drive architecture to control the GaN FET within the LMG341xR070. 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.

The integrated driver solves a number of challenges using GaN devices. The LMG341xR070 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 over-current and over-temperature 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. LMG3410R070 and LMG3411R070 have the same design and features, except the handling of OCP events. LMG3410R070 adopts a latch-off strategy at OCP events, while LMG3411R070 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 3rd quadrant of operation similar to a body diode but with higher voltage drop and higher conduction loss. 3rd 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 3rd quadrant operation is high; therefore, it is recommended to operate with synchronous switching and keep the duration of 3rd quadrant operation at minimum.