); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Don Collie wrote: > > Hi Bruce, > I`ve got the National Semiconductor Corporation Voltage Regulator > Handbook [1982]. On page 3-3, the leftmost graph shows the LM117/217/317 as > having its current limit, with a junction temperature of > 125 degrees Centigrade, at 2.25 Amps over the input/output differential of 5 > to 10 Volts. > The point being, that if you use a higher current regulator, you loose > the advantage of > the regulator`s current limiting, and perhaps, its thermal shutdown > protection as well. > A fuse *might* protect the semi`s down the line, but often it`s the > semi`s that fail before the fuse, and the peak current that might flow > before the fuse blows might be many times the current limit of the regulator > [which is nearly instantaneous], and if so, damaging, so it is wise to run > these regulators near their current limit, just as you would set the current > limit on a bench supply to just above the working current. > I find your use of the emotive words "inexperienced", "gullible", and > "cavalier" saddening. > Wishing you well,................................Don. > >
The graphs are only typical, read the actual printed specifications. You need to be more skeptical and question your assumptions. If you want a lower current limit regulator use an LM350. However you have identified one problem in applying 3 terminal regulators, the rather wide tolerances associated with the current limit circuitry. A 723 regulator can be easily designed to have a much narrower spread for the current limit. Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.