# EMI/ESD protection for USB interface?

I'm a student making a simple Arduino-compatible board similar to the Pro Micro and am going to put a USB connector on the board.

The schematic in the above link doesn't show any kind of EMI/ESD protection circuitry, and I've never used any in the previous boards I've made, but this time I did some research and found this is recommended.

I'm reading an Atmel application note giving recommendations for USB interfaces and it has the following:

There are a few similar questions on here, but I still am unsure of a few things:

• Should TVS or Zener diodes be used? The diodes in the Atmel application look like Zener diodes to me, but from what I've read is seems like TVS diodes would be more appropriate?
• How close should the breakdown voltage of the diodes be to 5V?
• How high do the voltage ratings of the diodes and capacitor need to be?
• Is the SHIELD pin shown on the diagram the "legs" of an SMD USB connector (i.e. the casing)?