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ADuM4160 Issues with EMI Radiation

Question asked by AME on Jun 4, 2018
Latest reply on Jun 4, 2018 by MSCantrell

Hello,

 

we use the ADuM4160 and recovered high EMI radiation during USB communication.
In our layout we followed the guidelines of AN0971:

 

Top (Layer 1)

 

GND-Planes (Layer 2)

 

GND-Planes (Layer 3)

 

Stitching Plane (overlap with both ground planes) (Layer 4)

 

The radiated noise with ADuM4160 looks like this:

 

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.


Regards

 

Adam
 

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