Automotive electronics suppliers today are taking greater advantage of the improved efficiency, quick power-switching capabilities, and smaller size of gallium-nitride (GaN) devices. The most recent development was the announcement by Transphorm that its third-generation high-voltage GaN FETs have passed the Automotive Electronics Council’s AEC-Q101 stress tests for automotive-grade discrete semiconductors. This marks the company’s second automotive-qualified product line and the first to perform at 175°C during qualification testing.
The TP65H035WSQA offers a typical on-resistance of 35 mΩ in an industry-standard TO-247 package. As with its predecessor—the 50-mΩ Gen II TPH3205WSBQA—the devices target ac-dc on-board chargers (OBCs), dc-dc converters, and dc-ac inverter systems for plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs).
The 650-V, 35-mΩ GaN FET, a normally-off device, combines high-voltage GaN HEMT and low-voltage silicon MOSFET technologies. Packaged in this configuration, the Si MOSFET and the GaN HEMT together behave as a single transistor—the GaN switch. The gate and the source of the GaN switch are given by the gate and the source of the Si MOSFET, while the drain of the GaN switch is given by the drain of the GaN HEMT. In Transphorm’s standard packages, the drain of the Si MOSFET, the source of the GaN HEMT, and the gate of the GaN HEMT aren’t accessible from the outside of the package.
Transphorm’s 650-V, 35-mΩ GaN FET follows the company’s 50-mΩ Gen II device.
Launched in June 2018, Transphorm’s Gen III devices came onto the market with the supplier’s claim that it was the highest-reliability, highest-quality [Q+R] GaN FETs available. They were said to offer the lower electromagnetic interference along with increased noise immunity (threshold voltage at 4 V) and gate robustness (at ±20 V), thereby producing quieter switching and higher performance at higher current levels with minimal external circuitry.
In choosing to conduct extended and accelerated JEDEC and AWC-Q101 standards testing, the semiconductor manufacturer stressed the devices’ thermal limits to 25°C more than those of the standard AEC-Q101-qualified high-voltage silicon MOSFET counterparts. Beyond proving the GaN platform’s robustness, Transphorm said the higher-temperature testing demonstrates that its AEC-Q101 GaN FETs will give design engineers ample thermal headroom when developing power systems.
In January, Transphorm released a validation data set for GaN power FETs in the 600-V and higher range including two new data types—Early Life Failure (ELF) and Field Failure—based on its having shipped over 250,000 GaN FETs as of December 2018.
“Proving device quality and reliability is perhaps the most critical factor influencing customer confidence in high-voltage GaN FETs—particularly in the automotive and electric vehicle markets,” says Philip Zuk, Vice President of Worldwide Technical Marketing, Transphorm. “To that end, we ensure that our GaN maintains its performance and reliability even in real-world conditions that may be far harsher than what mission profiles call for. As shown by the published reliability data, our JEDEC-qualified Gen III platform has a Field Failure FIT rate of 3, which is in line with that of silicon carbide. It’s this high reliability level that allowed Transphorm to release a Gen III automotive FET at 175°C.”