How to isolate the communication ground and power ground of a smart controller PAC?

Isolating the communication ground (e.g., Ethernet, CAN ground) and power ground (e.g., motor drive, power supply ground) of the PAC (Power Controller) is crucial to prevent noise coupling. A single-point connection between the communication ground and the system main ground is achieved using a ferrite bead (e.g., PBZ3216E120Z0T) or a 0Ω resistor, with the connection point near the power input. The communication interface circuits (e.g., PHY chip, transceiver) are powered by an isolated DC/DC module to achieve electrical isolation.

In the PCB layout, the communication ground area and power ground area are separated by an isolation strip of at least 5mm, with no copper foil inside the strip; slots are used if necessary. When communication signal lines cross the isolation strip, isolation devices (e.g., ADuM series digital isolators) or common-mode inductors (CMZ3225A-510T) are used. Tests show that this isolation scheme can reduce the noise voltage between the communication ground and power ground to less than 50mV, lowering the communication error rate by two orders of magnitude, and meeting the IEC61000-4-8 power frequency magnetic field immunity test requirements.