Where is the GND trace on a USB shield?
The location of the Chassis to PCB GND tab is on a sub-PCB, with a 30thou trace to the tab. (yes, I know it sounds strange, but the space constraints were ridiculous and this was not my design!) Firstly (as a bit of a cop out) personally, in designs I always ground through a 0R resistor so that the decision can be changed.
How are chassis GND and signal GND connected?
Chassis GND is connected to the metal case using mounting holes. Chassis GND and Signal GND are NOT connected together on the PCB, but instead use the metal case for that connection. The metal chassis is then eventually connected to the GND pin on the 3-prong AC power connector, NOT the neutral pin.
Is the USB shield supposed to connect to the ground?
In general, the USB host should connect the shield to ground (and earth, if possible). This is why the host side is typically expected to tie the shield to ground or earth.
What’s the difference between A and B USB cables?
USB cables have plugs, and the corresponding receptacles are on the computers or electronic devices. In common practice, the A end is usually the standard format, and the B side varies over standard, mini, and micro. The mini and micro formats also provide for USB On-The-Go with a hermaphroditic AB receptacle, which accepts either an A or a B plug.
How is the shield wire connected to the circuit ground?
For e.g. in case of USB powered devices, the USB cable has both a shield and a GND wire. The best practice is to have the GND (black wire) connected to the circuit ground. The shield wire (metal braid) gets connected to the chassis.
What is the purpose of grounding a shield?
It essentially grounds the shield while decoupling the noise that you’re concerned with. Well the only correct answer will depend from what do you really need to protect your system. I will try to cover most common situations although it will need a book to do that properly.