Using GaN HFET to replace MOSFET in DC/DC for space applications

To cope with space environment, radiation-hardened MOSFET switches are specifically designed in large dice (limiting their performance such as high parasitic capacitors compared to the ones designed for terrestrial application) and are packaged hermetically (SMDxx, TO25x,…). This leads to a high cost and large footprint, especially for DC/DC supplying high speed processors which require very low voltages and high currents (and consequently a lot of switches). Some GaN HFET designed for terrestrial applications have shown both good radiation robustness, small footprint and good intrinsic parameters (low Rdson and low parasitic capacitors). R&T activities have been done in cooperation with CNES (French Space Agency) to introduce GaN HFET, to put in place the screening process and to highlight the operating margins for space application. As the GaN HFET are massively produced for terrestrial applications, their intrinsic cost makes them attractive, even when space grade qualification has to be done (encapsulation in a hermetic package, screening, testing, burn-in …). Based on this work, Thales Alenia Space has developed and qualified a new generation of DC/DC converter for digital core using GaN HFET and is compared to a radiation hardened MOSFET solution.