How should the signal ground, analog ground, and power ground of a smart controller (PAC) be designed?

The signal ground (digital ground), analog ground, and power ground of the intelligent controller PAC need to be designed separately to avoid mutual interference.

First, the three areas should be separated in terms of physical layout, with the analog area (such as ADC and sensor interface) kept away from the switching power supply and digital noise sources.

Second, the analog ground, digital ground, and power ground should be connected in a single-point star connection at the power input using a ferrite bead (such as PBZ2012E600Z0T) or a 0Ω resistor to form a unified reference ground. The analog ground plane should be kept intact and independent, the digital ground plane should cover the high-speed signal trace area, and the power ground should use a large area of copper plating to reduce impedance. For high-precision analog circuits, isolation power modules (such as DC/DC isolators) can be used to achieve ground potential isolation.

Actual measurements show that this ground design strategy can improve the signal-to-noise ratio (SNR) of the PAC's analog circuit by 6dB, the bit error rate of the digital circuit by less than 10^-8, and pass the IEC61000-4-6 conducted immunity test.