How to avoid interference between analog and digital signals in I/O modules?

To avoid interference between analog and digital circuits within the I/O module, strict zoning and isolation are necessary. On the PCB layout, the analog and digital sections should be physically separated and placed in different areas of the board, separated by component-free isolation strips. Separate power and ground planes should be provided for analog and digital circuits. If a common ground plane is used, the ground planes of the analog and digital areas should be connected at a single point via a ferrite bead or a 0-ohm resistor; this point is typically chosen below the ADC/DAC chip.

Analog and digital power supplies should use separate LDOs or be isolated from the same switching power supply via ferrite beads. All signal lines crossing the analog-to-digital boundary must be isolated or filtered, for example, using digital isolators or RC filters. High-speed digital signals such as the ADC/DAC clock should be kept away from analog input/output pins. In the stack-up design, analog circuits can be placed on one side and digital circuits on the other, using the intermediate ground plane as shielding. Near-field scanning can be used to observe noise coupling and allow for targeted addition of shielding or layout adjustments.