Hi,
We have built a lot of 10 PCBAs. 4 seem to exhibit a strange failure: 5V output does not come up, and all 4 PCBAs have pins 7 (FB) and 8 (SS) shorted. one of the PCBAs also has VOUT and GND shorted.
Verified short is inside the LMZ by lifting (desoldering) pin 7 off the PCBA and checking for short with pin 8.
The remaining working 6 PCBAs measure 100-300K Ohms between pins 7 and 8.
We've built a previous batch QTY 25 of previous revision of the same PCBA, with the same power circuits, and didn't have any problems like this.
Any suggestions?
Thank you!
Michael
