SNOSCY4E March 2015 – October 2018 LMG5200
The LMG5200 device brings ease of designing high power density boards without the need for underfill while maintaining creepage and clearance requirements. The propagation delays between the high-side gate driver and low-side gate driver are matched to allow very tight control of dead time. Controlling the dead time is critical in GaN-based applications to maintain high efficiency. HI and LI can be independently controlled to minimize the third quadrant conduction of the low-side FET for hard switched buck converters. A very small propagation mismatch between the HI and LI to the drivers for both the falling and rising thresholds ensures dead times of < 10 ns. Co-packaging the GaN FET half-bridge with the driver ensures minimized common source inductance. This minimized inductance has a significant performance impact on hard-switched topologies.
The built-in bootstrap circuit with clamp prevents the high-side gate drive from exceeding the GaN FETs maximum gate-to-source voltage (Vgs) without any additional external circuitry. The built-in driver has an undervoltage lockout (UVLO) on the VDD and bootstrap (HB-HS) rails. When the voltage is below the UVLO threshold voltage, the device ignores both the HI and LI signals to prevent the GaN FETs from being partially turned on. Below UVLO, if there is sufficient voltage (VVCC > 2.5 V), the driver actively pulls the high-side and low-side gate driver output low. The UVLO threshold hysteresis of 200 mV prevents chattering and unwanted turnon due to voltage spikes. Use an external VCC bypass capacitor with a value of 0.1 µF or higher. TI recommends a size of 0402 to minimize trace length to the pin. Place the bypass and bootstrap capacitors as close as possible to the device to minimize parasitic inductance.