I am looking to power a PIC microcontroller with a supply voltage that ranges from 4.5V to 18V.
This will be a battery powered device so I would like to conserve power, ie. linear regulators like the 7805 is less desirable.
Also the application will be producing quite a bit of heat in an enclosed space so no need to add to heat generation with the linear regulator dissipating excess voltage.
After some hunting I suppose I am after a switch mode DC-DC converter, a step down one.
I have been looking at an LM2575 based circuit, but wondering what Vout would be if my supply Vin drops below the minimum 7V for regulation. The PIC I am working with have an operating range of 2V to 5.5V so I am OK with Vout being equal to Vin when Vin < regulation threshold.
So my question is, what happens to Vout when Vin < regulation threshold?
Also are there any additional things/circuits I should be considering?