AnsweredAssumed Answered

PB137ACV Problem

Question asked by alexander.david on Sep 24, 2013

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.