How to separate the signal ground and power ground of the I/O module?

In I/O module PCB design, proper separation of signal ground and power ground is crucial for noise control. Digital signal ground, analog signal ground, and high-current power ground should be physically separated into different areas. The separation gap is typically 0.5mm to 2mm. Connections between different ground planes should be made through a single point, usually chosen at the ground terminal of the power input filter capacitor. Connection methods can include 0-ohm resistors, ferrite beads, or direct narrow bridge connections. Ferrite beads, such as the PBZ series, provide isolation at high frequencies while conducting under DC conditions.

Analog ground should be kept clean, connected only to the analog ground pins of the ADC/DAC and the filter capacitors of the analog power supply. Power ground is noisier and should be set up separately for high-current circuits such as motor drives and relays, with a short and wide return path. All ground separations should be based on current return path analysis to ensure that high-frequency return current does not cross the separation gap, otherwise radiation will occur. After separation, numerous ground vias should be used to properly connect each ground plane. Finally, the separation effect should be verified through ground noise measurement and radiated emission testing.