How can I protect the USB pins on my Silicon Labs USB device from Electrostatic Discharge (ESD) events?
To protect the USB pins D+, D-, and VBUS from ESD events, we recommend using Transient Voltage Suppressor (TVS) diodes that are designed for the high bit-rate requirements of USB. You should make sure that the ESD protection device that you choose has a low capacitance and meets USB rise/fall time requirements. When making a selection, please note that Silicon Labs' CP210x USB-UART bridges are USB 2.0 Full Speed (12 Mbps) devices. Also note that Silicon Labs' USB microcontrollers can operate either at USB 2.0 Full-Speed (12 Mbps) or USB 2.0 Low-Speed (1.5 Mbps), depending on your firmware design.
Here are some ESD pin protection device part numbers that are designed for use with USB:
California Micro Devices PACDN043Y4
Cooper Industries 0603ESDA
Here are some resources that provide information on designing ESD protection specific to USB:
Littlefuse Application Notes [PDFs]: EC606, EC630, EC631
California Micro Devices Application Note [PDF]: AP-220
Author of the book 'USB Complete' Jan Axelson's USB Central page [Scroll down to the 'ESD and Overcurrent Protection for USB' section].