[Soekris] net4801 DC INPUT

[Jussi Peltola]

Hi,

On Wed, Dec 19, 2007 at 06:38:52PM +0100, Antoine Zen Ruffinen wrote:
> Having a close look to my net 4801, it seem that it use a LM2642 witch 
> is a step-down switching regulator. The datasheet of it 
> (http://www.national.com/ds/LM/LM2642.pdf) says that the maximum input 
> voltage of it is 30V. But if you have a doubt between two maximum value, 
> use the lowest one ! Anyway, in general, giving the lowest input voltage 
> to a regulator that you can (but not to close from the lowest limit), is 
> a good idea. it will ask less effort from the regulator.

In my experience switching regulators run much cooler at high input
voltages (less current through the switch because of the higher
voltage).

That's probably the reason desktop PC's use 12V for the CPU regulator
(the other being the required thickness of wires/traces with today's CPU
power requirements, making low input voltages impractical).

-- 
Jussi Peltola