On Wed, Apr 22, 2009 at 3:16 PM, solarwind wrote: > Hello everyone, > > I have a few of these chips: > http://datasheets.maxim-ic.com/en/ds/MAX667.pdf (MAX667 LDO Linear > Voltage Regulator). According to the datasheet, it says it has a > default fixed voltage output of 5 volts. The voltage input can be > anywhere from 3.5 to 16.5 volts. > > So lets say I leave it at the default 5 volts output. What happens to > the voltage output if I decrease the input voltage to 4 volts, for > example? > > Will the output be exactly 4 volts? Or does it work a different way? It will be lower by the "dropout voltage". LDO means "low dropout voltage". The datasheet will tell you what to expect. > > Also, I read a bit on voltage regulators on Wikipedia > (http://en.wikipedia.org/wiki/DC_to_DC_converter). It says: > > "They are very inefficient if the voltage drop is large and the > current high as they dissipate as heat power equal to the product of > the output current and the voltage drop; consequently they are not > normally used for large-drop high-current applications." > > Does this mean that they are inefficient if I supply a high voltage > (like 16 V) and and have a large current load (like 200 mA)? > then the regulator will be dissipating (16-5)*(200m) watts or 2.2 watts. You can use the C/W figures from the datasheet to tell you how many degrees warmer 2.2 watts will make your circuit. Or, you can build it and burn your thumb on it. I've done both ways. Regards, Mark markrages@gmail -- Mark Rages, Engineer Midwest Telecine LLC markrages@midwesttelecine.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist