Electrostatic protection method

- Feb 26, 2019-

1. Avalanche diode for electrostatic protection

This is also a method often used in design. A typical approach is to connect an avalanche diode to the ground in a critical signal line. The method utilizes the ability of avalanche diodes to respond quickly and has stable clamping, which can consume the accumulated high voltage in a short period of time to protect the board.

2, using high voltage capacitors for circuit protection

This method usually places a ceramic capacitor with a withstand voltage of at least 1.5KV at the position of the I/O connector or key signal, while the connection line is as short as possible to reduce the inductance of the connection line. If a capacitor with low withstand voltage is used, it will cause damage to the capacitor and lose its protection.

3, using ferrite beads for circuit protection

Ferrite beads can attenuate ESD current well and also suppress radiation. When faced with two problems, a ferrite bead will be a very good choice.

4, spark gap method

This method is seen in a material consisting of a layer of micro-belts made of copper, which is made up of triangular copper with pointed ends. The triangular copper is connected at one end to the signal line and the other is copper. Connected to the ground. When there is static electricity, a tip discharge is generated to consume electrical energy.

5, using the LC filter method to protect the circuit

The filter composed of LC can effectively reduce the high frequency static electricity entering the circuit. The inductive reactance of the inductor is very good at suppressing the high-frequency ESD from entering the circuit, and the capacitor shunts the high-frequency energy of the ESD to the ground. At the same time, this type of filter can also round the edge of the signal with a small RF effect, and the performance aspect has further improved in signal integrity.

6, multi-layer board for ESD protection

The choice of multi-layer boards is also a means of effectively preventing ESD when funds permit. In multi-layer boards, ESD is more quickly coupled to the low-impedance plane due to a complete ground plane close to the traces, thus protecting critical signals.

7. Method of protecting the periphery of the circuit board

This method usually draws traces around the board without a solder layer. Connect the trace to the enclosure as conditions permit, and note that the trace does not form a closed loop, which avoids the introduction of a loop antenna and introduces greater trouble.

8. Circuit protection using CMOS devices with clamp diodes or TTL devices

This method utilizes the principle of isolation for board protection. Because these devices are protected by clamp diodes, the design complexity is reduced in the actual circuit design.

9, more decoupling capacitors

These decoupling capacitors have low ESL and ESR values. For low frequency ESD, the decoupling capacitor reduces the loop area. Due to the ESL effect, the electrolyte is weakened, which can better filter out high frequency energy. .

In short, although ESD is terrible, it can even have serious consequences. However, only by protecting the power supply and signal lines on the circuit, it is possible to effectively prevent ESD current from flowing into the PCB. Among them, my boss often said that "a good grounding of a board is king." I hope this sentence can also bring you the effect of breaking the skylight.

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