We are using TPS2350 in one of our designs .
In 3 of the 4 boards it is working fine, but one of the board is working fine when input is -48 V from AC-DC Supply but its output is fluctuating when DC-DC supply is used at input.
When connecting both AC-DC and DC-DC supplies it is working fine (giving -48V Output).
While probing pins of the IC in faulty board we got following results-
-48 V at pin 2, -48 V with fluctuations at pin 6 and pin 11, and -22 V WITH MAJOR FLUCTUATIONS at pin 13
While probing pins of the IC in WORKING board we got following results-
0 V at pin 2, -38 V at pin 6 and pin 11, and -48 V at pin 13
Attached is the snapshot of our design
Regards,
Hammad