How to suppress common-mode interference when multiple serial ports on an edge computing box are working simultaneously?

When multiple RS232/RS485 serial ports on an edge computing box operate simultaneously, common-mode loop interference can easily form due to cable ground potential differences. Solutions include:

1. Using an independent isolated transceiver, such as the ADM2682, with an isolation withstand voltage of 2500Vrms to block ground loops.

2. Connecting a TVS array ESDSM712 in parallel to ground at the bus port. The SM712 has dual shutdown voltages of 7V and 12V and a junction capacitance of 5pS to suppress surges and common-mode spikes.

3. Connecting a common-mode inductor CML3225A-510T in series with each serial port. The CML common-mode inductor 3225 has dimensions of 3.2×2.5mm, and the 510T has an inductance of 51μH, providing high common-mode impedance in the 1-30MHz range.

4. Using shielded twisted-pair cables with the shield connected to signal ground at one end.

With this configuration, the bit error rate of 8 serial ports communicating simultaneously at full load is <10^-9, and the common-mode voltage is suppressed to within ±2V.