20737S VBat short to GND

Hi,

I set 20 pcs of 20737S based system to test overnight yesterday. Everything worked fine until this morning.

When I checked again around noon, I found the temperature of 1 of the 20 pcs is high. Then, check the VBAT pin voltage, found it is short to GND. So, I detach the 20737S from main board and check again. Confirm the VBAT is short to GND. It's difficult to know what happens, because others are still working after 1 day functional test. Is there any suggestion? Should I return the chip for analyzing?

Thanks,

Brian