How to pass the EFT test for the I/O module?

Ensuring I/O modules pass the Electrical Fast Transient (EFT) test requires design considerations for their high-frequency, high-energy characteristics. EFT protection filters must be installed at all external connection ports, including power, communication, and I/O ports. Typical configurations include common-mode chokes, such as the CML series, and safety-certified Y capacitors to bypass common-mode noise to ground. At power ports, additional X capacitors and differential-mode inductors are needed. For signal ports, RC filters or ferrite beads can be added after the TVS diodes. PCB layout is crucial; port filter grounds must be connected to a clean "quiet ground," which is connected to the internal circuit ground via a single point to prevent noise from directly coupling into the system. Internally, additional local LC filters should be provided for the power supplies of sensitive components such as the CPU and ADC. For digital inputs, Schmitt triggers combined with software debouncing are used. For communication interfaces, frame checking and timeout retransmission mechanisms should be included in the protocol at the hardware level. During testing, noise on critical signals and power lines must be monitored to identify and optimize coupling paths. Multiple iterations and improvements are often required to pass higher levels of EFT testing.