I am working on a circuit that uses an Atmel AVR in a speed controller
for an R/C airplane. The AVR and R/C receiver are powered by an
LP2986IM 5 volt linear low dropout regulator.

Once the battery gets down to 6 volts it's supposed to cut off the
motor. When I tried it the motor stopped, the red light went on, and
the regulator started smoking! It draws about 400 mA which is the
short-circuit limit for the regulator. It gets very hot and I can't
leave it on more than 1 or 2 seconds. Also the output voltage rises
to 5.7 volts, which is (or close to) the input voltage (and enough to
possibly wreck the AVR). The strange part is it's fine until the voltage
drops under 6 V or so. (I raised the cutoff setting and it was fine).

Does anyone have any idea what's wrong with this thing? Right now I'm
afraid to test it too much; everything is SMT and I don't really want
to build another one.

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body