Static electricity is everywhere, especially in electronic products. It is the most common. So what can be done to prevent static electricity problems?

Let me take you to analyze the tips for preventing static electricity damage to TVS tubes. Rapid ESD pulses may cause damage to circuit boards. An induced voltage is generated between adjacent (parallel) conductors. If this happens, the induced voltage path will become another path for the surge to reach the IC since it will not be protected. Therefore, protected input lines should not be placed next to other separate, unprotected traces. The recommended PCB layout scheme for ESD suppression devices should be: filter out interference signals from all I/O ports as much as possible, close to the connector/contact PCB side.

When wiring, try to shorten the connections between high-frequency components as much as possible, and try to reduce their distribution parameters and mutual electromagnetic interference; the wires used at the input and output ends should try to avoid adjacent parallel lines. It is best to add a ground wire between the lines to avoid feedback coupling.

While using TVS tubes to protect against ESD damage, it must be coordinated with a reasonable PCB layout. The first thing is to avoid self-feeling.

For sudden pulses such as ESD, it is likely to cause parasitic self-inductance in the circuit, which will cause a strong voltage impact on the circuit and may exceed the IC's endurance limit and cause damage. The self-inductance voltage generated by the load is proportional to the intensity of the power supply change, and the transient characteristics of ESD shocks can easily induce high self-inductance. The basic principle of reducing parasitic self-inductance is to shorten the shunt loop as much as possible. All factors including the ground loop, the loop between the TVS and the protected line, and the path from the interface to the TVS must be taken into consideration. Therefore, the TVS device should be as close as possible to the interface and to the protected line, so as to reduce the chance of self-inductance coupling to other adjacent lines.

In summary, the following principles should be followed when wiring TVS tubes:

1. The differential signal lines should be as short as possible to reduce the distributed capacitance on the PCB traces, and should always be parallel and equal in length, with line spacing equal to twice the line width, and ground covering measures should be taken as much as possible;
2. The PCB traces connected to both ends of the TVS tube must be larger than 10mil to prevent overcurrent generated by surges from burning the printed lines;
3. Avoid running critical signal lines near protection lines;
4. Try to arrange the interfaces on the same side;
5. Avoid parallel connection of protected circuits and unprotected circuits;
6. The area surrounding the loop formed by various signal lines and their feeders should be as small as possible. If necessary, consider changing the position of the signal line or grounding line;
7. Connect the TVS tube interface signal line and grounding line directly to the protection device, and then to other parts of the circuit;
8. Keep reset, interrupt, and control signals away from the input/output ports and away from the edge of the PCB;
9. Add grounding points wherever possible;

About Semiware
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