How to shield the interference of the switching input of a power FTU?

Interference from digital inputs can cause misjudgments, requiring hardware filtering and shielding. An RC filter (10kΩ + 100nF) with a 1ms time constant is used to eliminate jitter. A parallel ESD protection device (5V0D8B) is connected to the input port for bidirectional ESD protection. Shielded twisted-pair cables are used for the signal lines, with the shield grounded at the FTU terminal. PCB layout: Digital input circuits are centrally located, away from interference sources. Optical isolation, such as the TLP281, is used, with an isolation voltage of 2500Vrms. Software debouncing: resampling is performed after a 10ms delay. This shielding improves the immunity of digital inputs, reducing the false positive rate to less than 0.001%, meeting the IEC 61000-4-4 EFT 4kV test requirements.