Visit：2052   Date：2019-12-26

The circuit board is grounded primarily through the power cord. One wire of the three-wire plug is the ground wire, so the ground wire on the circuit board can be connected to the power wire ground wire in the power supply design.
The control system should be grounded at one point. In general, high-frequency circuits should be grounded at multiple points nearby, and low-frequency circuits should be grounded at one point. In low-frequency circuits, the inductance between the wiring and the components is not a big problem. However, the interference caused by the loop formed by the ground is very large, so one point is often used as the ground point.
However, one point of grounding is not suitable for high frequency, because at high frequency, there is inductance on the ground wire, which increases the impedance of the ground wire, and inductive coupling occurs between the local wires. Generally speaking, if the frequency is below 1MHz, you can use one point to ground; when it is higher than 10MHz, use multiple points to ground; between 1-10MHz, you can use one point to ground, or you can use multiple points to ground.

Extended information:
Common ground processing for digital and analog circuits
Many PCBs are no longer a single function circuit (digital or analog circuit), but are composed of a mixture of digital and analog circuits. Therefore, when wiring, you need to consider the interference between them, especially the noise interference on the ground.
The frequency of digital circuits is high, and the sensitivity of analog circuits is strong. For signal lines, high-frequency signal lines are as far away from sensitive analog circuit devices as possible.
For the ground wire, the entire PCB has only one node to the outside world, so the digital and analog ground issues must be handled inside the PCB, and the digital ground and the analog ground are actually separated inside the board. The connection is only at the interface where the PCB is connected to the outside (such as a plug, etc.).
The digital ground is shorted to the analog ground. Please note that there is only one connection point. There are also non-common grounds on the PCB, which is determined by the system design