I am not clear on the issue here. Can you elaborate? What is the issue?
You have FAULT and SD tied together in the schematic so if the voltage on SD is going low it is likely being pulled low by FAULT trigger. FAULT can trigger due to short circuit (OC) or DC detect. Can you check that DC is filtered out of the signal post input DC blocking caps and that the current is within operating spec of the device?
PCB图纸顶层
PCB底层图纸
PCB图纸
可能是干扰问题，不知道应该怎么改进？