Electronic equipment, electronic devices and the increasing frequency of the processor, the electronic system is a multi-component and many subsystems of complex devices. High density and high speed will cause the system to increase the radiation, and low pressure and high sensitivity will reduce the system immunity. Therefore, electromagnetic interference (EMI) is a threat to the safety of electronic equipment, reliability and stability. Our design of electronic products, PCB board design to solve the EMI problem is essential. This article mainly explains the PCB design should pay attention to the place, thereby reducing the PCB board electromagnetic interference problem.

Definition of electromagnetic interference (EMI)

Electromagnetic interference (EMI), can be divided into radiation and conduction interference. Radiation interference is the source of interference to the space as a media to interfere with its signal to another electrical network. The conduction interference is to use the conductive medium as a medium to interfere with the signal on an electrical network to another electrical network. In the high-speed system design, the integrated circuit pins, high-frequency signal lines and all kinds of plugs are common in the PCB board design radiation interference sources, they emit electromagnetic waves is electromagnetic interference (EMI), itself and other systems will be affected normal work.

Design of PCB for electromagnetic interference (EMI)

Today's PCB board design techniques have a lot of solutions to solve the problem of EMI, such as: EMI suppression coating, the appropriate EMI suppression parts and EMI simulation design. The above video describes ways to reduce EMI. Now let's take a brief look at these tips.

Tip 1: Common mode EMI interference source (eg voltage drop across the power supply bus to form a transient voltage at both ends of the inductor at the decoupling path)

- In the power layer with a low value of the inductor, the inductance of the synthesis of the transient signal will be reduced, common mode EMI to reduce.

- Reduce the length of the power supply to the IC power supply pin.

- Use 3-6 mil PCB layer spacing and FR4 dielectric material.

Skill two: electromagnetic shielding

- try to put the signal on the same PCB layer, and close to the power layer or ground plane.

- The power plane should be as close as possible to the ground plane

Skills three: the layout of parts (different layout will affect the circuit interference and anti-jamming capability)

(Such as demodulation circuits, high-frequency amplifying circuits and mixing circuits, etc.), in which different strong and weak electrical signals are separated, and digital and analog signal circuits are separated

- The filter network of each part of the circuit must be connected in the near future, which not only can reduce the radiation, which can improve the anti-interference ability of the circuit and reduce the chance of being disturbed.

- Disruptive parts should be avoided in the layout of the interference source, such as data processing board CPU interference.

Tip 4: wiring considerations (unreasonable wiring will cause cross-interference between the signal lines)

- can not have the border close to the PCB board frame, so as to avoid disruption caused by the production.

- the power cord should be wide and the loop resistance will be reduced.

- the signal line is as short as possible and the number of vias is reduced.

- Corner wiring can not be used in the right angle method, should be 135 ° angle is better.

- digital circuits and analog circuits should be ground isolation, digital ground and analog ground to be separated, and finally connected to the power ground

Reduce electromagnetic interference is an important part of the PCB board design, as long as the design to go to the side of the idea, naturally in the product test, such as EMC test will be more qualified.