We seem to have a problem with the UCC3957-2:
With this circuit which is almost identical to Fig.2 in the datasheet, except for some added protection resistors.
this is our board layout, which should not have excessive trace length to any critical components or other factors leading to unstable operation?
Power FETs and current sensing resistor are located on the bottom side of the board, made necessary ba the small size that is permitted for the board.
Now, the 4-cell battery pack is connected according to the datasheet info, negative terminal first, then positive and then all 3 taps. After connecting the topmost tap to AN1, the series resistor on this pin burns out. We tested the same with a second board, with identical outcome. After replacing the resistor, the UCC3957 does not work at all anymore.
After looking around some message boards, other users seem to have the same problems, so it may not be caused by a fault in our board?
the UCC3957 was obtained as a sample from TI, so it should not be a counterfeit or otherwise defective component, and normal ESD precautions were always observed.
Is there a known problem with the UCC3957, and a possible solution?