Hi,
We are using the TPS65261 as a power converter in our inspection camera design. On the first cut of the board, there were absolutely no issues with the part. There has never been a failure. Now on the next board revision, with the only change being adding a second ground and second power plane, the LX1 output shorts to ground instantly. Component placement around the chip did not change from the first to second rev.
Do you have any ideas as to what sort of conditions would cause this?
The LX1 output is 9.6V supply, basically unloaded at powerup. LX2 is a 10.3V supply, unloaded at powerup. LX3 is the 3.3V supply for the system. All operate off a primary 12V supply, which ramps from 0 to 12V in about 5ms with no noticeable overshoot or undershoot.
I have populated the TPS65261 power supply on the new board by itself -- it works fine with an external supply.
The 12V supply on the board has a 100uF ceramic on the output, and this supply connects to the TI supply directly through surface connections and two sets of parallel planes, over just a few mm. Could the 12V supply be too stiff?
Paul
