Nexperia has launched its second generation gallium nitride (GaN) technology, taking on silicon carbide in mid-range electric vehicle applications.
The H2 650V GaN FET is a cascode device, combining a high mobility HEMT GaN-on-silicon transistor with a low voltage silicon MOSFET in a single package. This reduces the complexity of designs by allowing a simple silicon driver to be used, says Michael LeGoff, general manager for GaN at Nexperia and the former managing director of Plessey Semiconductor. "This means it is very simple to drive with a 15 percent improvement, it's a big improvement," he said.
Packaging is a key element for automotive designs and the H2 is initially packaged in a TO-247 with an on resistance RDS(on) of 41 mΩ (max 35 mΩ typ. at 25 °C). However a version in the company’s proprietary CCPAK copper clip surface mount packaging is planned which gives an RDS(on) of 39 mΩ (max 33 mΩ typ. at 25 °C). Replacing the internal bond wires with copper clips reduces parasitic losses, optimizes electrical and thermal performance and improves reliability. The CCPAK GaN FETs are available in top- or bottom-cooled configurations to improve heat dissipation.
Future optimisations of the process and package will see RDS(on) falling to under 20mΩ for 100kW designs, says LeGoff. The third generation will cut that in half to 10mΩ.
The device is aimed at on-board chargers and DC-DC converters, taking 400V from the battery pack in mid-range electric vehicle designs direct to a 12V rail without intermediate steps. The company is looking at 900V and 1200V GaN devices that can be used with 800V systems in the future, says LeGoff.
The first generation H1 GaN parts were used in a demonstrator inverter design with Ricardo: NEXPERIA TEAMS WITH RICARDO ON INVERTER DEMONSTRATOR
The new GaN technology at Nexperia uses through-epi vias to make a connection to the back of the silicon substrate.