Using GaN as secondary-side FET with InnoSwitch4-QR

Posted by: alberto.mari.m… on 02/19/2026

Hi team.

This is a general question.

Would it be possible to use a 150V or 200V GaN FET that has a low-Rdson (few milliOhms) at Vgs=4V as secondary-side FET with the INN4276C?
I would like to know if there are any possible drawbacks.

Thanks.

Comments

Hi Alberto,

150V is possible. However, when powering up, we only recommend have a breakdown voltage 90% of 150V since the absolute maximum voltage that the FWD pin can handle is only 150V. Beyond this may damage the IC.

Furthermore, Rds(on) of the Mosfet is also critical parameter. Too low or high may cause false triggering during the switching cycle. I would suggest reviewing/checking the design guides of our InnoSwitch. This will give you a good start when identifying the FET needed in the secondary. See page 20-21 for your reference.

an-72_innoswitch3_family_design_guide_20251107.pdf

Regards,
PI Nanoe

Ok thanks.

So, for confirmation: we can use GaN FETs for the secondary-side rectification, provided that they comply with the requirements of AN-72. Correct?

Hi Alberto,

Body diode is a critical information for our innoswitch products. So GaN FETs are not recommended. Thank you.

-Gavin