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LM5116: LM5116 does not work normally when it is just powered on

Part Number: LM5116

Dear team,

My customer is using LM5116 in a 48 Vin, 12 Vout buck circuit, but now they found 2% ratio board damage issue in their end customer.

The phenomenon that the my customer reproduced is when first powered on, the drive signal of Q15 is only larger than 3V, after 3us the Q15 is broken, LM5116's VCCX and VCC are all shorted to ground.

See the screenshot for the reproduced waveform, yellow represents Q15's DS, green represents Q15's GS, blue represents output voltage, and we can get that Q15's GS was only 2.8V before the switch tube was broken.

Please see schematic, PCB, mos datasheet as below. 

So can you tell the possible reason of this phenomenon an how to solve this problem? Please share your suggestions, thanks in advance!

 2451.PCB.xlsx6354.schematic.pdf0434.Mos datasheet.pdf