We will be submitting an Apalis SOM based product (custom carrier) for regulatory testing shortly and have opportunity to update the design in preparation for manufacturing introduction. In none of the eval designs nor the Ixora carrier design, do the HDMI signals have any common-mode chokes in the differential pairs to the HDMI receptacle. As there is no mention of EMC measures for either the DVI or HDMI reference within the Apalis Carrier Board Design Guide (V1.5), our carrier design reflects this approach.
Can you confirm, either through your own testing and/or through feedback from customers, that EMC compliance is achievable without common-mode filtering, initially for the TK1 based SOM but possibly also for the IMX8 based SOM as well? Our experience with HDMI 2.0 designs has made us wary of EMC difficulties with certain TMDS transmitters, and we were forced to implement chokes for regulatory compliance. Although the TK1 supports HDMI 1.4b, possible future Apalis SOM variants may support HDMI 2.0. Would the inclusion of filter chokes on the carrier not be a form of future-proofing, or will EMC compliance measures always be incorporated in the SOM itself?