Q: What are the EMC requirements for automotive electronics (ISO 7637 and CISPR 25)?
Answer
Automotive EMC requirements: (1) ISO 7637-2: conducted transient immunity (load dump 100 us spike pulse 1a/1b etc.). Key: add TVS diode on 12V supply (UNCLAMPED 40V for 12V system) and bulk capacitor (1000 uF) near the input. (2) ISO 7637-3: radiated transient immunity (via capacitive coupling clamp). (3) CISPR 25: radiated emissions (30 MHz-1 GHz) – stricter than commercial. Use shielded cable for all wiring. (4) ISO 11452: component-level radiated immunity (100 V/m for some applications). (5) ISO 10605: ESD for automotive. Design practices: (1) All PCB layers: use solid ground plane. (2) Supply filtering: feedthrough capacitor at PCB entry point. (3) Transient protection: TVS on every external connector. (4) PCB shield: solder-down EMI can over MCU and radio section. (5) Cable routing: keep sensitive cables away from ignition wires by >10 cm. (6) Automotive-grade components rated to 125C minimum. (7) Use Automotive Ethernet (100BASE-T1) for in-vehicle networking to reduce cable EMC issues.
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