I was looking over my raspberry pi model B and I noticed a resistor between the USB power connector shield and ground. I've noticed this on many PCB designs with much larger packaged resistors although I've never known the reason for them.
This is the part I'm curious about, R51.
On the board, it looks like its an 0805 package, although I've seen larger one.
So my questions are basically:
- Why do we need a resistor here? is it something to do with ESD when inserting a cable into the connector?
- Why do we use such a large package? I assume its to handle more power, but where would this power come from since they are both "GND"
Please correct me if I'm wrong in any of my thinking