LTC3892-1 in DRVcc=5 configuration has a gate drive current of around 510mA instead of 2A

I used LTC3892-1 as a 20A output 32V -> 12V DCDC converter. I have the DRVSET set to 50k, so the DRVcc is 5V. The circuit was also simulated in LTSpice and seemed to be correct.

The configuration is:

DRVUV = 49.9K (5V)

FREQ = 54.9k (350kHz)

GaNFETs = EPC2206, 19nC charge / 5V at the gate

My rise time is 37ns vs 10-20ns estimated/simulated. The measured peak gate current (diff probe at 0.1 Ohm shunt at BG) is around 510 mA. How do I increase the drive strength?

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  • Hi,

    1) I don't use external FET drivers, I use LTC3892-1 in DRVcc=5V to drive them, there is not much difference in how GaN FETs are driven beside the gate voltage.

    2) Even with the Development board for LTC3892 I am getting only 1.2A peak driving current, comparing to the LTspiceXVII\examples\jigs\3892.asc, where even if I add parasitics it shows 2A.

    I am trying to figure if the issue is in datasheet/simulation model or is there some configurations issues, like EXTVcc, that I am missing, which would degrade the performance of the gate driver.