A Flip-Chip Capable Low-Side and High-Side SOI Gate Driver with Variable Drive Strength for GaN Power FETs

Abstract

A variable drive strength gate driver for gallium nitride (GaN) power FETs intended for a 6.6 kW EV charger is presented. The driver incorporates low-side and high-side channels in a single integrated circuit that is flip-chip capable. The gate driver has been designed in a 0.18 μm silicon-on-insulator (SOI) process featuring deep trench isolation, 1.8 V and 5 V CMOS devices, and DMOS devices rated up to 200 V. The on-chip protection circuitry includes an undervoltage lockout (UVLO) in both channels, desaturation detection, and a VDS sensing circuit for the low-side power FET. The novel VDS sensing implementation enables the gate driver to have a dynamically controlled source current, programmable between 0.15 A and 2.4 A, to mitigate excessive ringing. Both low and high-side channels have a sink current of 5 A. The gate driver IC also includes active Miller clamping, a low-side to high-side level shifter, and a power supply for each channel.