Hi,

We are doing a 430W Sync Buck.
Vin = 55.5V, Vout = 48VDC, Fsw = 325kHz, Power = 430W.

It uses a TO220 synchronous FET.

So we put a 60V Zener to protect the 60V rated Switching node pin of the LT3763 (as shown)
from overvoltage spikes.
How do you like it? Does it work for you?

LT3763 datasheet:
https://www.analog.com/en/products/lt3763.html

(As you can see, its all bog standard stuff, so no secrets here)

(LTspice and PNG files attached)

 

need TVS diode, supressor. ideal on cut/off 50volts: SAC50 https://www.vishay.com/docs/88379/sac.pdf

 

Vin = 55.5V

Using a 60V max part at 55.5 is cutting it close. How accrete is the 55.5? +/- 5%?

A SOD123 diode seems small for limiting the input. (low power)
56V+/-5%.
The diode is good for 85mA DC or 2.3A for 8mS.
If the spike is short term, you might think about a LC filter at the input. The L C might eat up most of the spike.
What happens if the Vin is 5% high and the diode is 5% low?

Looks like the duty cycle is very high.

I think D3 is not doing anything. It is not a fast diode.

The MOSFETs are 60V and you are using them at 60V. Hope they work.

It appears you are using the to-220 mosfets at 325kHz. I think you should look at surface mount with no leads.