The generation of interference sources refers to the components of the PCBA board, and the incorrect circuit design during wiring, and the vibration generated after being energized with other circuits. The layout of the components is reasonable. At this time, the PCB board layout is 50% completed, and the next step is the circuit design routing.
1: The position of the entire power supply circuit needs to be considered during PCBA layout, and the low-voltage circuit and high-frequency circuit need to be far away from the power supply circuit. If there is enough space, the ruler may isolate the low-voltage GND and power GND circuits.
2: In the circuit, motors and noise-prone circuits need to be controlled by MCU I/O, and isolation circuits should be added to the I/O ports and motors and devices that are prone to noise.
3: Attention should be paid to the wiring of the crystal. When the MCU has an external crystal, it is necessary to check that the crystal is close to the MCU during layout. At the same time, the bottom of the crystal cannot be made of a whole piece of copper, which will cause frequency deviation, and an isolation ground needs to be added.
4: On the circuit board, it is necessary to divide the circuit of the whole board before layout, which can be divided into AC/DC area, DC area, power supply bottom voltage circuit, control area, high frequency area, and easy to generate interference source area. Layout in the MCU It is necessary to stay away from the above areas and use as much ground as possible to isolate.
5: In the ground isolation mode, there are power ground, high voltage and analog low voltage ground. The high voltage ground and the bottom pressure ground need to be isolated by an optical couple. Analog low-voltage ground and digital ground need to be processed by inductors or isolation chips.
6: The MCU and the device with relatively large power need to be grounded separately, which can reduce the interference generated during the operation of the device and affect the stability of the MCU.
7: At the MCU power supply pin, a filter circuit needs to be added. The filter circuit includes LC and other circuits. At the same time, it is equipped with a combination of high-frequency capacitors and bottom-frequency capacitors to increase the stability of the MCU and enhance anti-interference.