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HDMI EMI issues, i.MX6 DualLite

Question asked by Magnus Loven on Mar 25, 2015
Latest reply on Sep 7, 2015 by Magnus Loven



I have encountered EMI issues on HDMI on my custom iMX6 DL board. My HDMI interface is the same as in the Sabre design with the CM2020 as ESD/level shifter.


The peaks i measure is at 65MHz, 130MHz, 325MHz. The 65MHz reach as high as 40dBuV. I have patched in common mode filters (Murata DLP11SN900HL2L) on the diff pairs between the CM2020 and the HDMI connector and ferrite beads (Murata BLM18HE102SN1D) on the rest of the HDMI signals without any improvement.


Simply turning off (or pulling the HDMI cable at the monitor side) the monitor will completely quiet the EMI issues.


I have tried several different HDMI cables. I found 1 cable with slightly better performance. I also tried different monitors/TVs but no improvement.


My board is a 8 layer with the following stackup:

1 signal

2 gnd

3 signal

4 pwr

5 signal

6 signal

7 gnd

8 signal


The HDMI diff pairs are carefully routed (impedance matched) on layer 1 between HDMI connector, CM2020 and to the iMX6 edge. Then on layer 8 a short bit and then up through vias to the iMX6.


Has anyone used the CM2020 with good EMI results?


Any input on this would be appreciated.