we use the ADuM4160 and recovered high EMI radiation during USB communication.
In our layout we followed the guidelines of AN0971:
GND-Planes (Layer 2)
GND-Planes (Layer 3)
Stitching Plane (overlap with both ground planes) (Layer 4)
The radiated noise without ADuM4160 looks like this:
We tried to reduce the noise with the following measures:
- Adding a common mode choke (90R @ 100 MHz) to the D+/D- lines on the primary side
(Wurth Electronic 744231091).
- Adding a shield made of copper to the top and the bottom side of the PCB and connect it with GND on the secondary side.
- Replacing the 10R resistors on the VBUS1 and VBUS2 terminals by 0R.
- Adding 2p7 capacitors between data-lines (D+/D-) and GND.
-Adding a 2p7 capacitor between D+ and D-. This reduced the Level of the Peaks (please notice the changed scale of the y-axis):
Our question is what measures we can take to solve our issue.