How should the interface circuit of a Human-Machine Interface (HMI) be laid out to reduce interference?

Optimizing HMI interface circuit layout to reduce interference requires a compact and effective design in terms of filtering, isolation, and grounding. Interface circuits include physical layer transceiver circuits such as RS485, CAN, Ethernet, USB, and HDMI. The core principle of the layout is "blocking noise at the port." All interface connectors should be concentrated on one side or corner of the PCB for easy unified handling. Immediately behind each interface connector, its corresponding protection and filtering circuitry should be placed, such as TVS diodes, common-mode chokes, filter capacitors, and isolation transformers/optocouplers. These components should be placed as close as possible to the connector pins. The interface chip itself should be close to these protection and filtering circuits, minimizing the length of sensitive signal lines.

The ground plane of the interface circuit should be single-point connected to the digital main ground plane via a ferrite bead or a 0Ω resistor, or a separate "clean ground" should be partitioned off in the interface area for the interface chip and filtering components. Interface signal traces should be as short as possible and avoid crossing digital noise areas. For high-speed interfaces such as Ethernet, differential correspondences should be strictly routed according to differential rules and kept away from other signals. The metal housing of the interface connector should be connected to the PCB chassis ground through multiple low-impedance points. This compact, isolated layout, combined with EAST Electronics' ESD/TVS, common-mode chokes, and other devices, minimizes the intrusion of external interference and the escape of internal noise.