How to separate power and signal for I/O modules

Effectively separating power and signal components in I/O modules is fundamental to preventing conducted coupling interference. In terms of physical layout, power modules, filter inductors, and large-capacity capacitors should be grouped together in one area of the PCB, while signal processing chips and interface circuits should be placed in another area, with gaps in between. In terms of layer stack-up, if possible, power planes and ground planes should be placed on different layers, using intermediate layers for isolation.

When routing, power traces should be wide, and signal traces should be thin, avoiding long parallel runs. If parallel runs are unavoidable, maintain a spacing of at least three times the trace width, or insert a ground wire for isolation. Power lines should pass through decoupling capacitors before entering the chip to prevent power supply noise from coupling to the signal section through chip pins. For noise generated by switching power supplies, ferrite beads can be used to isolate the analog power pins from the digital power pins of the chip. At the system level, use separate cable trays or conduits to run power cables and signal cables separately. Near-field probes can be used to detect and optimize the coupling of power lines to nearby signal lines.