How is EMC performance during long-distance bus transmission for intelligent controllers (PACs)?

The EMC design for long-distance (>10m) transmission of the PAC bus for intelligent controllers needs to address attenuation, radiation, and interference. Shielded twisted-pair cable (e.g., CAT5e) should be selected, and both ends of the shielding layer should be grounded (if grounding at both ends may create a ground loop, capacitive grounding or single-end grounding should be used). A matching resistor (e.g., 33Ω) should be connected in series at the transmitting end, and a terminating resistor (e.g., 120Ω) should be connected in parallel at the receiving end. A common-mode inductor (CML3225A-510T) and TVS protection (SMBJ6.5CA) should be installed at the cable entry point.

For differential buses, differential drivers should be used, and pre-emphasis technology should be employed to compensate for high-frequency attenuation. In terms of layout, the interface circuit should be kept away from noise sources and powered by an isolated power supply. Testing has verified that this design enables the CAN bus to achieve a bit error rate of less than 10^-8 during 1000-meter transmission, and Ethernet to meet the IEEE 802.3 standard during 100-meter transmission, passing IEC61000-4-2 ESD 8kV and IEC61000-4-5 Surge 1kV tests.