We have many boards out TPS54335A in the field. We started experiencing random failures in the 5V line provided by this chip. The failure is that the PH pin gets nearly grounded (~5ohm resistance).
The 5V rail in most cases sees less than 100mA load and no more than 300mA peak. Here's a waveform at this pin:
Strangely, the 3.3V line, which is also driven by this chip, and whose design and layout is identical with the exception of the resistive divider, never fails. The 3.3V line carries a larger current.
What's killing this chip?
I see that in the post below, the OP suggests the problem may be related to a light load condition, which is exactly what we have:
