Posted on September 24, 2013 at 00:59Greetings:
I've apparently destroyed 3 of these, so time to appeal to a higher authority.
Circuit is same as application circuit in data sheet. Battery to charge is Amstron 12V 22Ahr SLA. Power supply is TDK-Lambda LS35-15 adjusted to about 17Vdc. Battery is nearly full (13.1V). Heat sink is 2.5'' x 2'' x 1'' extruded aluminum for TO220, screwed on tight, with thermal grease.
First time battery is connected, PB137 puts out about 1.25A, which rapidly falls off to about 200mA (10-15s). Nothing smokes, nothing gets hot, everything looks normal. Second time it's connected, current into cell goes up to about 2A, and part gets really HOT. Seems to be shorted. If I disconnect the battery and check the dc resistances between the pins, I get about 4 Ohms, vs about 40K Ohms out of the box.
I tried 3 parts, all three did the same thing. Data sheet says the part is ''essentially indestructible.'' I'm very curious to know what I'm doing to break them. Any help is appreciated.
#pb137acv
