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iMX8MQ HDMI failing in FCC Class B

Question asked by Ritesh Patel on Feb 19, 2020
Latest reply on Mar 22, 2020 by Ritesh Patel


We have used iMX8MQ processor on our custom board design. Currently going through a compliance testing. 

HDMI is giving a hard time to qualify the EMC certifications. Find attached image showing the results of radiated emission scan of our custom board with 1080p HDMI display.


Design summary:

- We followed all guidelines provided in Hardware design guide for iMX8M.

- The intra & inter pair for HDMI traces are 5 mil & 20 mils. 

- Impedance controlled to 100 ohm differential for all HDMI signals

- Routed in internal layer with continuous ground plane reference

- Added ground via close to differential signal vias

- Used EMI filter near to HDMI connector


We explored & came across few parameters which can help to get reduce the radiated emissions above, those are:

Slew rate, Voltage Swing, Drive strength and terminations. 

Want to know where we can tune above parameters using register settings in iMX8M.


Any help here would be greatly appreciated.