Hi all:
We have recently delivered a batch of products and found that a small part of the ULN2003A chip of the control relay may cause plate burning, which is quite serious. The unified part is the com foot of ULN2003A (the 9th foot of the chip burns out).We have done some destructive experiments, but did not restore this situation.
Would you please help to analyze under what circumstances the chip will burn down?
Thank you!
11 pin output waveform in normal operation:
Normal working 10-pin output waveform:
PCB placement: