pumping out 40A of lm5116

[carmusic]

Hi i need to design a step down dc converter (not isolated), i need voltage output from 1 to 48V at 40A, ive seen that lm5116 could do the job up to 20A, could i use bigger mosfet or parallel mosfet to go up to 40A with it? the gate peak charge of the lm5116 is 3.5A, is it enough to drive several mosfet in parallel?
Or could i use two lm5116 system and parallel them while monitoring current of each (this seems harder to do)
Ive found other isolated dc dc converter that would do the job but they cost me 700$! id rather developp one since i dont need isolation (will be powered from big solar panel system at approx 50V input
Thanx

 

[Hero999]

What's the maximum input voltage?

If it's just 50V, you could use a low drop-out linear regulator and it will be 96% efficient which is as good or better than most switched mode power supplies.

 

[ericgibbs]

What's the maximum input voltage?

If it's just 50V, you could use a low drop-out linear regulator and it will be 96% efficient which is as good or better than most switched mode power supplies.

The OP says: i need voltage output from 1 to 48V at 40A

How will this be 96% over its output range.????

 

[Hero999]

I missed that.

Yes, you're right, he'll be able to get 48V from 50V with a linear regulator at 96% efficiency but not 1V which will involve a switching regulator.

Well that makes things much more difficult.

To answer the question: the 3.5A only refers to the gate drive current, not the MOSFET current so it is more than capable of driving a higher powered MOSFET.

Check the datasheet, one of the circuits shows a 7A SMPS, see page 23.

https://www.electro-tech-online.com/custompdfs/2010/04/LM5116.pdf

 

[carmusic]

yes i know it is gate drive but in webbench on national website lm5116 is limited to 20A, i think i will try it with parralel mosfet and bigger inductor and double capacitor

 

[mneary]

The LM5116 does not actually limit your current, since the current doesn't flow through it. You might have a problem getting a dependable Rs (R11) of 0.003 ohms. But the LM5116 circuit will not work for you anyway since its output is only programmable from 1.215V to 80V and you need 1V. Take note also that with Vout/Vin being such a huge number, your inductor will be enormous. It will NOT be 6uH as the schematic on page 23.

What on Earth do you need 1V at 40A for?

 

[carmusic]

1.2V is ok, i dont need 40A at 1 volt, maybe 10A at voltage lower than 5V, i need those dc converter for solar cathodic protection system, the common dc converter use is often 0-48V 10A, but i need bigger than that