Chassis ground vs circuit ground connected to IO connectors

[Kostas_P]

Hi Robert,

I have been searching on Internet of which is the correct way of connecting the shielding pins of IO connectors such as USB, RJ45, HDMI etc..

Some people recommend to isolate chassis ground with circuit ground. I have checked your designs and i have observed that you connect the shielding pins of IO connectors to a common ground.

Have you ever experienced issues by connecting all IO connectors with a common PCB ground with regards to ESD or EMI?

Thank you!!

[robertferanec]

A difficult question to answer

The main reason why I connect the connector shielding on our CPU boards directly to board ground is, that it is connected this way on the reference boards (including reference schematics from companies like Intel or AMD). Also, we have seen better results when doing ESD testing.

However, the connection may depend on the kind of board you are designing and applications. For example, one of disadvantages of direct connection is, that if you are connecting boards which are far away from each other, there can be difference in Ground potential and when you connect these boards together, there may be current flowing between them.

So, if you are not sure, you can always separate the shield and board ground, but give option to place 0R resistors around the board to connect them together.

I hope this helps.