USB Easily get into Unrecognized Trouble

Jayce Luo

Hi TI expert,

Met hard issue here. After safety ground of the equipment is connected, the USB interface cannot be recognized by other devices. When the safety ground is disconnected, the USB can be recognized again.

No doubt that the safety ground introduces some noise, something that influence the USB device.

Have you met similar issue before? Do you have any solution to solve the issue? Any TI devices can handle such situation?

B R,

Jayce L

over 5 years ago

0 Brian Zhou over 5 years ago

TI__Guru**** 151810 points

do you use the same ground for USB connector shield and ground pin?

0 Jayce Luo over 5 years ago in reply to Brian Zhou

TI__Prodigy 590 points

No, connected through a 1nF 2kV High Voltage Capacitor.

0 Jayce Luo over 5 years ago in reply to Brian Zhou

TI__Prodigy 590 points

And the USB connector shield is connected to the PE(safety ground) of the equipment.

0 Brian Zhou over 5 years ago in reply to Jayce Luo

TI__Guru**** 151810 points

you may need to monitor the noise on safety ground and connector ground and try to separate them

0 Jayce Luo over 5 years ago in reply to Brian Zhou

TI__Prodigy 590 points

Hi Brian,

How should I monitor the noise? And how can I separate them?

Should I separate the safety ground and the connector ground? Can I add magnetic beads or resistor between the safety ground and the connector ground?

Is there any article or materials that can be a reference for this case?

B R,

Jayce L