Hi John,
A couple more things:
- Can we get Part nos for the input and output caps used? We recommend X5R or X7R ceramic type. See Data Sheet Pg. 9
- It seems that the pass FET inside the device fails short and from the description the part is permanently damaged, correct? If the Output voltage ever goes above the input voltage, the body diode in the pass FET will conduct and could be damaged. Not sure if this could happen at any point during extended time operation. Are their any step load changes during the test?
- To test the above, is it possible to cut traces (or is there a connection to 3.3 V plane?) from the supply output to the load and just load the supply with a resistor and run another extended time test to see if the device fails?
- The schematic and layout look OK except they may need more vias to connect between the power pad and the board GND. The thermal resistance with one via may be too high to dessipate the heat.
- The device power pad is soldered to the board solder pad correct? See pg. 14 of the data sheet for WSON package thermal considerations and layout.
- Can they measure In to Out resistance of damaged devices to see if the pass FET is shorted?