Electromagnetic compatibility refers to the ability of electronic equipment to work harmoniously and effectively in various electromagnetic environments. The purpose of electromagnetic compatibility design is to enable electronic equipment to suppress various external interference, enable the electronic equipment to work normally in a specific electromagnetic environment, and to reduce the electromagnetic interference of the electronic equipment itself to other electronic equipment.
Use the correct routing strategy
Using equal routing reduces the inductance of the wires but increases the mutual inductance and distributed capacitance between the wires. If the layout allows, it is best to use a well-shaped mesh wiring structure. The specific method is to use horizontal wiring on one side of the circuit board and vertical wiring on the other side, and then use metallized holes to connect at the cross holes.
Choose a reasonable line width
Since the impact disturbance of the transient current on the printed circuit is mainly caused by the inductance component of the printed circuit, the inductance of the printed circuit should be reduced as much as possible. The inductance of a printed line is directly proportional to its length and inversely proportional to its width, so short and thin wires are beneficial to suppress interference. Clock leads, line drivers, or bus driver signal lines often carry large transient currents, and printed wires should be kept as short as possible. For discrete component circuits, when the width of the printed line is about 1-5mm, it can fully meet the requirements. For integrated circuits, printed line width can be between 0-2-1-0mm.
Avoid electromagnetic radiation caused by high-frequency signals passing through printed conductors
In order to avoid electromagnetic radiation generated by high-frequency signals through printed wires, the following points should be noted when wiring the circuit board: 1- The bus driver should be close to the bus to be driven. For leads leaving the board, the driver should be close to the connector. 2- The data bus wiring should be sandwiched between every two signal wires. It's best to place the ground loop next to the least important address lead, since the latter usually carries high-frequency currents. 3- Minimize the discontinuity of printed lines, for example, the line width should not change, and the line angle should be greater than 90 degrees to prevent loops. 4-The clock signal lead is most likely to produce electromagnetic radiation interference. It should be close to the ground circuit when running, and the driver should be close to the connector.
Suppress crosstalk between PCB lines
In order to prevent circuit board traces from crossing, long-distance equidistant traces should be avoided during wiring design, trace spacing should be as far apart as possible, and signal lines should not cross with ground wires and power lines. line as much as possible. Crosstalk can be effectively suppressed by placing a printed line between some signal lines that are very sensitive to interference.
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