Industry's first 100-V half-bridge gate driver for enhancement-mode GaN power FETs

June 20, 2011 // By Paul Buckley
National Semiconductor has introduced what the company claims is the industry’s first 100 V half-bridge gate driver optimized for use with enhancement-mode Gallium-Nitride (GaN) power field-effect transistors (FETs) in high-voltage power converters. National’s LM5113 is a highly-integrated, high-side and low-side GaN FET driver that reduces component count by 75 percent and shrinks printed circuit board (PCB) area by up to 85 percent compared to discrete driver designs.

Designers of power bricks and communications infrastructure equipment require high power efficiency in the smallest form factor. Enhancement-mode GaN FETs enable new levels of efficiency and power density compared to standard metal-oxide semiconductor field-effect transistors (MOSFETs) due to their low on-resistance (Rdson) and gate charge (Qg) as well as their ultra-small footprint, but driving them reliably presents significant new challenges. National’s LM5113 driver IC eliminates these challenges, enabling power designers to realize the benefits of GaN FETs in a variety of popular power topologies.
Meeting the stringent gate drive requirements of enhancement-mode GaN FETs requires multiple discrete devices and significant circuit and PCB design effort.  National’s LM5113 fully-integrated enhancement-mode GaN FET driver greatly reduces circuit and PCB design effort and delivers industry-best power density and efficiency.
National’s LM5113 is a 100 V bridge driver for enhancement-mode GaN FETs.  Using proprietary technology, the device regulates the high side floating bootstrap capacitor voltage at approximately 5.25 V to optimally drive enhancement-mode GaN power FETs without exceeding the maximum gate-source voltage rating.  The LM5113 also features independent sink and source outputs for flexibility of the turn-on strength with respect to the turn-off strength.  A low impedance pull down path of 0.5 Ohms provides a fast, reliable turn-off mechanism for the low threshold voltage enhancement-mode GaN power FETs, helping maximize efficiency in high frequency power supply designs. The LM5113 features an integrated high-side bootstrap diode, further minimizing PCB real estate.  The LM5113 also provides independent logic inputs for the high-side and low-side drivers, enabling flexibility for use in a variety of both isolated and non-isolated power supply topologies.

National’s LM5113 is offered in a 10-pin 4 mm by 4 mm LLP package and cost $1.65 each in quantities of 1,000.  Samples are available now and production quantities will be available in September 2011.
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