How To Drive Rad Hard E-Mode GaN Transistors Efficiently And Safely

Focus:

Radiation hardened (rad hard) eGAN HEMT devices offer the space power system designer a vastly improved Ciss * RDS(ON) figure-of-merit as well as much faster switching times compared to rad hard silicon MOSFETs, but have different gate-drive requirements. This article explains the factors that influence the choice of the correct gate-source voltage in a space application and how to account for them in designing gate-drive circuits. The authors explain why Freebird Semiconductor recommends a 4.2-V gate-drive level for optimum efficiency and a 6-V absolute maximum. Next they discuss how device packaging and the source-sense connection help to manage switching transients at the gate terminal. The discussion continues with explanations and simulation of the effects of device characteristics and pc-board parasitics on these transients, demonstrating the effects of loop inductance on the overshoot seen at device turn-on and the use of damping resistance to limit this overshoot. The impact of device characteristics and pc board parasitics on device turn-off are also discussed and demonstrated. The use of different internal values of pull-up and pull-down resistance within integrated gate drivers is explained. Tips are offered on selection of the damping resistance value, sizing of the source sense connection and other layout considerations.

What you’ll learn:

• How to design gate-drive circuits for rad hard eGaN HEMTs in space power applications

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Author & Publication:

Tony Marini and Jim Larrauri, Freebird Semiconductor, Haverhill, Mass., How2Power Today, Nov 15 2019

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