So, you can use digital converter MP8854 (DATASHEET), 2.85V - 18V, 4A, High-Efficiency, Wide-Input, Synchronous, Step-Down Converter with Integrated Telemetry via I2C Interface.
It has efficiency about 95% at 2A output current.
It can work without using I2C interface if you do not need dynamically change of output voltage value.

Thank you. Yes, I already see that.
But I need dynamically change of output voltage value, because this is for the input of the FPGA.
So, what do you mean about 12C?

 

So, what do you mean about 12C?

I2C - it is interface between your microprocessor and digital converter.
Digital converter will change its output voltage by commands from microprocessor.
ADDED:
I2C Communication Protocol

I would like to know for example the difference between MP8854 and LTM4623, the Input from power Step down converster ist 5 V, and the Output is 1.2V with 2A output current requirment.

LTM4623 - 1.2V sets by feedback resistor, efficiency 87%, Multiphase Operation - yes, External Frequency Synchronization - yes, can not be digitally controlled.
MP8854 - 1.2V sets by feedback resistors, efficiency 95%, Multiphase Operation - no, External Frequency Synchronization - no, can be digitally controlled.

 

Please elaborate. I don’t know what an MPS converter is. What are you converting? Signals? Or power?

Thank you for your reply,

I would like to know for example the difference between MP8854 and LTM4623, the Input from power Step down converster ist 5 V, and the Output is 1.2V with 2A output current requirment.
There is a fpga board for camera.
And I thought that I could be make conceptional general questions.
I didn't know that it isn't a good way to ask a general question.

 

Thank you for your reply,
And I thought that I could be make conceptional general questions.
I didn't know that it isn't a good way to ask a general question.

It is quite acceptable to ask a general question and so you got a general answer to it. The rest of the posts here are the result of misinterpretation of your wording. Most hi-tech guys are very analytical (including me) and so some of them do a lot of nit-picking before they come up with an answer, which is not necessarily a bad thing!

 

It is ok to ask a general question, but as they say, "the devil is in the details".