Switching Regulator Power Supply

Hi All,

I need to design and build the circuit and printed circuit board to receive the power. I have got 40 volts input and I do not know how much input current because the guy who is working on it still experiemnt with his part of the system.

The load or the circuit needs atleast 4 volts and 400mA current to work properly. I thought that I can convert the 40 volts downto 5 volts or so using the following buck regulator

and then using the following Power Controller and Li Ion charger to toggle between charging the Li-ion battery or providing the Load circuit with LT3970 's DC 4 volts output. Am I right?

My questions and problems are as follows

1. Am I going in the right direction with this?

1. What I understood from the LTC4055's data sheet is that I do not need to use the pins "IN1" and " IN2" because I have only one input and I can use "Wall" input pin for the input voltage that ranges between 2 to 40 volts. But If I go with Wall pin than what would be the status of the following pins a. HPWR b.CLPROG c.ACPR d. Susp

I would appreciate if someone gives a good advise.

Thanks John