LTC3862-2 is used in 12v, 33v input, output 48v 7A, When the 12v input,The output power of LTC3862-2 can reach the maximum 350w?
in principle yes, but you have to be aware of the (peak) current requirements for delivering 350W with 12V input. Inductor, shunt and FET parameters play a vital role. On top layout and thermals should be done with great care. Take a look at the Democircuit DC2006A-A, which delivers 500W(50V, 10A) max for an input range from 6V-36V. The board configuration allows for a output power derating below 9V:
So the two phases should work for your app with 12V as minimum input voltage.