Why TVS transient suppression diodes can effectively protect against ESD static damage

Why TVS transient suppression diodes can effectively protect against ESD static damage

Static electricity is ubiquitous, especially in electronic products. So what are the ways to prevent static electricity problems? Let me take you to analyze the clever ways of TVS s to prevent static damage. Fast ESD pulses may generate induced voltage between adjacent (parallel) wires on the circuit board. If the above situation occurs, as it will not be protected, the induced voltage path will become another path for surges to reach the IC. Therefore, protected input lines should not be placed next to other separate, unprotected wiring. The recommended layout plan for ESD suppression device PCB should be to 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 wiring 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 terminals should be avoided from being adjacent and parallel as much as possible. Add ground wire between wires to avoid feedback coupling.

When using TVS s to protect ESD damage, it is necessary to cooperate with a reasonable PCB layout. The first thing is to avoid self perception. For a sudden pulse like ESD, it is likely to cause parasitic self inductance in the circuit, which can form a strong voltage surge on the circuit and potentially exceed the IC's tolerance limit, causing damage. The self induced voltage generated by the load is directly proportional to the intensity of power supply changes, and the transient characteristics of ESD impact are easy to induce high-strength self inductance. The basic principle of reducing parasitic self inductance is to minimize the shunt circuit as much as possible, taking into account all factors including the grounding circuit, the circuit between TVS and the protected line, and the path from the interface to TVS. So TVS devices should be as close as possible to the interface and the protected circuit, in order to reduce the chance of self inductance coupling to other adjacent circuits.

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

1. The differential signal line should be as short as possible to reduce the distributed capacitance on the PCB wiring, and always maintain parallelism, equal length, and line spacing of twice the line width, and try to adopt grounding measures as much as possible;

2. The PCB wiring connected to both ends of the TVS  should be ensured to be greater than 10mil to prevent overcurrent generated by surges from burning out the printed wire;

3. Avoid using critical signal lines near protective lines;

4. Try to arrange the interfaces on the same side as much as possible;

5. Avoid parallel connection between protected circuits and unprotected circuits;

6. The surrounding area of the circuits formed by various signal lines and their feeders should be as small as possible, and if necessary, the position of the signal line or grounding wire can be considered to be changed;

7. Connect the TVS  interface signal line and grounding line directly to the protective device, and then enter other parts of the circuit;

8. Keep reset, interrupt, and control signals away from the input/output ports and the edges of the PCB;

9. Add grounding points wherever possible.