We have implemented LM5166X in a brushless motor controller design that uses a 36V battery (42V fully charged). The 5V output from LM5166X draws at most 100mA, but in Webench I specified 500 mA for future needs. See schematic below (basically taken directly from Webench). Note we are not currently using C35 or C36. They are just placeholders.
We have built 12 first articles with this new design. All tested ok initially. One tested ok in our manufacturing, but when it got to our customer, it didn't power up correctly. Customer reported a buzzing sound, and measured an output resistance of around 3 Ohms on the 5V line (indicating a short). Also the 5V line when powered only measured around 1.5V. I am not sure if the short is internal to LM5166X or somewhere else in the system, but wanted to ask if the short is internal what could cause it to fail this way? Does everything in my schematic look ok? Does the buzzing sound give any clue to what may have gone wrong?
any advice would be appreciated.
