Hey,
we are using the LED Driver IC LT3763 with Mosfets since serval years to drive high power UV LEDs (Vf ~20V Iled ~ 14A).
For a new version of the LED Driver, we want to switch to GaN Fets so that we can reduce the PCB size and achieve faster switching times.
From the datasheet of the LTC780 which you use for the EPC9141 reference design the driver stage looks like the LT3763 stage.
If we use the same additional components (Zener diode, resistor between intvcc and boost pin) do you think that we can use GaN Fets with the LT3763?
Do we need to take something else into account?
Many thanks
Best Christoph
Hi Christoph,
Thank you for writing in. Yes, you are correct: it does look like LT3763 can be made to work well with GaN FETs, with the circuit modifications that you refer to.
For the others reading: Refer to the LTC7800 data sheet, Fig. 14 on page 29. There are 3 small additions that allow this controller (and LT3763’s driver looks similar) to work well with GaN FETs: 1) small 10 ohm R in series with the boost diode, 2) small zener in parallel with the boost capacitor, and 3) a small schottky in parallel with the bottom FET. The purpose of the Schottky is not for efficiency, but rather to limit the negative voltage on the switch node during dead time (some/many controllers need this limit).
Also: if you don’t already have series gate drive resistors, you may want to add them. Even 0 ohm jumpers would be good. This will allow you to slightly slow down the very fast GaN FETs, in case that is needed.
Thanks again for your question!
Brian Miller, field applications engineer, EPC
Hey,
thanks for the fast response.
All your recommendations are already included.
Would it be possible to share with you over mail our layout to minimize the risk for issues?
Best Christoph
That is great, sounds like you are making good progress. The best way start a review: contact EPC’s European team, because I think you are in Europe? If so, the European sales manager can set you up with your local field application engineer. The sales manager’s email address: Stefan.Werkstetter@epc-co.com
best regards, Brian (in USA, east coast)