Leveraging Special Dead-Time Control Modes To Optimize GaN-Based Buck Converter Designs
by James R. Staley, Analog Devices, Durham, N.C., How2Power Today, Sep 15 2025
Focus:
This article explores the switching dynamics at play when GaN FETs are used in place of
silicon MOSFETs for the power stage in synchronous buck converters and how specialized
dead-time adjustment modes in two buck controllers—the LTC7891 and LTC7890—can be used to
optimize dead time based on design goals for efficiency and reliability. The article
begins by discussing differences in silicon MOSFET and GaN FET structures and how they
affect reverse recovery and associated losses, reverse conduction losses, and deadtime
requirements for GaN. The specialized deadtime adjustment modes in the LTC7891 and LTC7890
are explained. The article then discusses probing and layout requirements for verifying
deadtime performance, considerations in selecting gate resistance, and selection and usage
of the three specialized deadtime adjustment modes.
What you’ll learn:
- How to understand the differences in deadtime requirements for GaN FETs versus silicon MOSFETs
- How to measure GaN FET switching waveforms
- How to apply specialized deadtime control modes in the LTC7891 and LTC7890 synchronous buck controllers
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