What is ESD protection diode? Its working principle and selection method

What is ESD protection diode? Its working principle and selection method

Elertro Static Discharged Protection, also known as ESD, is an overvoltage and anti-static protection component designed for I/O port protection in high-speed data transmission applications. This article has collected and organized some materials, hoping to have significant reference value for readers.

What is ESD protection diode? ESD in the electronics industry originally meant electrostatic discharge, but now it can be extended to mean anti-static, electrostatic protection, and other meanings. ESD diode, static electricity and discharge are the same. The principle of ESD protection for diodes is that when the voltage exceeds the conduction voltage of the diode, it will conduct and discharge to the ground. Normal signals cannot reach the conduction voltage and will not be lost through ground. However, when the ESD voltage exceeds the conduction voltage, it will be discharged to the ground to prevent damage to the internal components.

Working principle of ESD diode

When there is no abnormal interference in the system, the ESD electrostatic protection diode can be ignored and has no effect during normal operation. But when the external interface voltage exceeds the breakdown voltage of the ESD diode, the ESD diode begins to function and diverts the current to ground.

There are three types of ESD models, namely Human Body Model (HBM) ESD (designed for chip production, assembly, and transportation processes), Charged Device Model (CDM) ESD (designed for chip production, assembly, and transportation processes), and IEC61000-4-2 ESD (designed for daily use). Among them, IEC61000-4-2 level is the daily contact level, which is normally divided into 4 levels:

Level 1: Contact discharge voltage of 2KV, air discharge voltage of 2KV

Level 2: Contact discharge voltage 4KV, air discharge voltage 4KV

Level 3: Contact discharge voltage 6KV, air discharge voltage 8KV

Level 4: Contact discharge voltage 8KV, air discharge voltage 15KV

Selection method of ESD diode

So, the key question is, with so many ESD diodes, how to choose the right one?

1) Calculate the range of interface signal amplitude to determine the operating voltage of ESD protection products.

2) Determine the use of unidirectional or bidirectional ESD electrostatic protection diodes based on the signal type. The advantage of a single channel bidirectional ESD diode is that it can be grounded at any pin, providing convenience for design.

3) Determine the maximum acceptable parasitic capacitance of the interface based on the signal rate. The higher the signal rate, the smaller the junction capacitance of the ESD diode is required.

4) Select the appropriate clamping voltage based on the maximum withstand voltage impulse of the circuit system;

5) Ensure that ESD diode protection products can meet or exceed IEC 61000-4-2 level 4

I believe that by reading the above content, everyone has gained a preliminary understanding of ESD protection diodes. At the same time, I hope that everyone can make good summaries during the learning process, so as to continuously improve their professional level.