Jussi Peltola wrote: > 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).
~30-80amps for a core 2 at 1.3volts would be painful to distribute directly from an offboard power supply or on the 3.3volt rail like a pentium... _______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
