I have been designing a PCB which includes an SD card connector. As I'm not a PCB designer expert, I was looking for a reference design when I came across with the circuit bellow, extracted from Texas Instruments
My question is about the purpose of the capacitor (C206, 0.1uF) tied between GND and MicroSD_earth (Chassis Ground). Other reference designs seldom includes that capacitor, and usually the chassis ground pins are tied directly to GND of the PCB or left floating. Whats the correct way to go and why? I'm really confused.
1) Tie SD connector metallic shield pins directly to the ground (PCB GND);
2) Tie them to the ground with a capacitor, like depicted in the figure shown above;
3) Left shielding pins floating.