Eval Board Sch - why all four power transistors have different part numbers?

Question

why the eval board shows four different FET devices (four different part numbers) on the output power driver? see screen shot below 
 
 Thank you 
 
 Fausto Bartra

John_M · Answer

I see you have a duplicate post.

I am still waiting on confirmation but it is most likely the FETs are optimized for the specific location in the design. You could use the same FETs but they need to meet the criteria for the use case.

John_M · Answer

Technically you can use the same MOSFET for all four positions on LTC3777. The controller just drives quad N‑FETs with similar gate drive, so there’s nothing preventing that electrically. That said, it’s usually not optimal because the devices don’t all see the same loss profile — depending on VIN, VOUT, duty cycle, and load, some FETs spend more time switching large voltages while others are carrying more continuous current. One group is more switching‑loss dominated (Qg, Crss), while the other is more conduction‑loss dominated (RDS(on)). Using the same FET everywhere basically forces a compromise between those two, which shows up as lower efficiency and higher thermals. It’s fine for simplicity or early bring-up, but for a cleaner/optimal design you’d normally split them based on how they’re actually being used.

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Eval Board Sch - why all four power transistors have different part numbers?