- Issue Time
- Feb 21,2022
This article will share some points that need to be paid attention to in the design of the ground wire of the printed circuit board for your reference.
In the design of printed circuit boards, grounding is an important method to control interference. The correct combination of grounding and shielding can solve most interference problems. The ground wire structure in the printed circuit board roughly includes system ground, chassis ground (shield ground), digital ground (logic ground), and analog ground. In the design of the ground wire of the printed circuit board, we should pay attention to the following points:
1. Correctly choose single-point grounding and multi-point grounding
In the low-frequency circuit, the operating frequency of the signal is less than 1MHz, the inductance between its wiring and the device has little influence, and the circulating current formed by the grounding circuit has a greater influence on the interference, so one point grounding should be used. When the signal operating frequency is greater than 10MHz, the impedance of the ground wire becomes very large.
At this time, the impedance of the ground wire should be reduced as much as possible, and the nearest multi-point grounding should be used. When the operating frequency is between 1 and 10MHz, if one-point grounding is used, the length of the grounding wire should not exceed 1/20 of the wavelength, otherwise, the multi-point grounding method should be used.
2. Separate digital circuits from analog circuits
There are both high-speed logic circuits and linear circuits on the printed circuit board. They should be separated as much as possible, the ground wires of the two should not be mixed, and they should be connected to the ground wires of the power supply. To maximize the ground area of the linear circuit.
3. Try to thicken the ground wire
If the ground wire is very thin, the ground potential will change with the change of the current, resulting in an unstable timing signal level of electronic equipment and deterioration of anti-noise performance. Therefore, the ground wire should be thickened as much as possible so that it can pass the allowable current on the printed circuit board. If possible, the width of the ground wire should be greater than 3mm.
4. Form a closed loop with the ground wire
When designing the ground wire system of the printed circuit board composed of only digital circuits, making the ground wire into a closed-loop can significantly improve the anti-noise capability. The reason is that there are many integrated circuit components on the printed circuit board, especially when there are components that consume a lot of power.
Due to the limitation of the thickness of the ground wire, a large potential difference will be generated on the ground junction, causing the anti-noise ability to decrease. , If the grounding structure is formed into a loop, the potential difference will be reduced and the anti-noise capability of the electronic equipment will be improved.
In the grounding design of the PCB board, the grounding technology is applied to both multi-layer PCB and single-layer PCB. The goal of grounding techniques is to minimize the ground impedance, thereby reducing the potential of the ground return from the circuit back to the power supply.
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