I have read some articles about USB ESD protection and followed the suggestion to add TVS Diode Array USB6B1 in my design. However, my design is still failed to pass the ESD test and I don't know where the problem is.
This is the testing procedure and result:
Inject electrostatics on the product's metal surface, which is connected as the GND of the PCB.
-- The USB transceiver reboot and USB connection break.
Inject electrostatics on the USB port's shield.
-- Same result as step1.
This is the circuit about USB protection. The power source of the board isn't from the USB, so the VBUS output pin is floating.