Q: How to design EMC-compliant USB and HDMI interfaces on PCB?
Answer
USB 2.0 EMC design: (1) Route D+/D- as 90 Ohm differential pair over solid ground reference plane. (2) Place ESD protection (USBLC6 series) within 5 mm of the connector with short wide traces to ground. (3) Add common-mode choke (500 Ohm @ 100 MHz) on the connector side of the cable for radiated emissions. (4) Use shielded connector shell with 360-degree connection to board ground. (5) Decouple USB power pin (VBUS) with 10 uF bulk + 100 nF ceramic near the connector. (6) Place series resistors (22-33 Ohm) on D+/D- if the host controller does not have built-in series termination. USB 3.0 additionally requires: shielding reference plane continuity and coupling/decoupling networks on TX/RX pairs. HDMI EMC: similar approach with differential 100 Ohm pairs 90 Ohm HDMI. Add HDMI-specific common-mode filters. Use HDMI connector with integrated shielding.
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