PCB Technical - pcb factory: common measures to cut off the interference propagation path

PCB factory: common measures to cut off the interference propagation path

1. Fully consider the impact of the power supply on the microcontroller. If the power supply is done well, the anti-interference of the whole circuit will be solved more than half. Many single-chip microcomputers are very sensitive to power supply noise, so it is necessary to add a filter circuit or voltage regulator to the single-chip power supply to reduce the interference of power supply noise to the single-chip microcomputer. For example, magnetic beads and capacitors can be used to form a π-shaped filter circuit. Of course, 100Ω resistors can be used instead of magnetic beads when the requirements are not high.

2. If the I/O port of the single-chip microcomputer is used to control noise devices such as motors, isolation should be added between the I/O port and the noise source and a π-shaped filter circuit. To control noise devices such as motors, isolation should be added between the I/O port and the noise source, and a π-shaped filter circuit should be added.

3. Pay attention to the crystal oscillator wiring. The crystal oscillator is as close to the pins of the microcontroller as possible, the clock area is isolated with a ground wire, and the crystal oscillator shell is grounded and fixed. This measure can solve many difficult problems.

4. The circuit board is reasonably partitioned, such as strong and weak signals, digital and analog signals. Keep interference sources such as motors, relays, and sensitive components such as single-chip microcomputers as far away as possible.

5. Separate the digital area from the analog area with a ground wire, separate the digital ground from the analog ground, and finally connect it to the power ground at one point. The wiring of A/D and D/A chips is also based on this principle. Manufacturers have considered this requirement when assigning A/D and D/A chip pin arrangements.

6. The ground wires of the single-chip microcomputer and high-power devices should be grounded separately to reduce mutual interference. Place high-power devices on the edge of the circuit board as much as possible.

7. The use of anti-interference components such as magnetic beads, magnetic rings, power filters, and shields in key places such as the I/O port of the single-chip microcomputer, power line, circuit board connection line, etc., can significantly improve the anti-interference performance of the circuit.

2. Improve the anti-interference performance of sensitive devices

Improving the anti-interference performance of sensitive devices refers to the method of minimizing the pickup of interference noise from the side of sensitive devices and recovering from abnormal conditions as soon as possible.

Common measures to improve the anti-interference performance of sensitive devices are as follows:

1. Minimize the area of the loop loop when wiring to reduce induced noise.

2. When wiring, the power wire and ground wire should be as thick as possible. In addition to reducing the voltage drop, it is more important to reduce the coupling noise.

3. For the idle I/O ports of the single-chip microcomputer, do not float, but should be grounded or connected to the power supply. The idle terminals of other ICs are grounded or connected to power without changing the system logic.

4. The use of power supply monitoring and watchdog circuits for single-chip microcomputers, such as IMP809, IMP706, IMP813, X25043, X25045, etc., can greatly improve the anti-interference performance of the entire circuit.

5. On the premise that the speed can meet the requirements, try to reduce the crystal oscillator of the single-chip microcomputer and select low-speed digital circuits.

6. The IC devices should be soldered directly on the circuit board as much as possible, and IC sockets should be used less.

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