Static electricity is an objective natural phenomenon, which will cause damage and damage to electronic products, resulting in functional disorders and even damage to components of electronic products and equipment. So the ESD protection device was born, so what is the ESD protection device? Today, let's focus on ESD protection devices and other components.

1、 What are ESD protection devices?

ESD electrostatic protection components are designed to protect the O port of Imax for high-speed data transmission applications.

ESD electrostatic protection components RLESD protection devices can prevent sensitive circuits in electronic equipment from being affected by ESD. It provides very low capacitance and better transmission line pulse (TLP) testing and IEC6100-4-2 testing capabilities than other similar components, especially after multiple samples (up to 1000). This device can provide lower trigger voltage and lower clamp voltage than traditional polymer SEO devices, thus improving the protection of sensitive electronic components.

Electrostatic Protection element (ElertroStatic Discharged Protection) is referred to as ESD, which is a kind of overvoltage protection device, which is designed for the protection of Icano port in high-speed data transmission applications. RLESD protection devices are used to prevent sensitive circuits in electronic equipment from being affected by ESD (electrostatic discharge). Can provide very low capacitance, excellent transmission line pulse (TLP) testing, as well as IEC6100-4-2 testing capabilities, especially after the multi-sampling number is up to 1000, thus improving the protection of sensitive electronic components.

The commonly used ESD protection devices are mainly Diode, Resistor, P/NMOS, BJT, SCR and so on. Because of their avalanche breakdown, avalanche and injection characteristics, they can instantly enter the low resistance state, so they have good current discharge capacity and can be used as ESD protection devices.

2、 ESD protection device classification

ESD protection devices mainly fall into four categories: TVS diodes, varistors, multilayer chip capacitors (MLCC), and ESD suppressors. The application scenarios of each device are also different. The following are the characteristics of several protection devices.

1. For MLCC, MLCC mainly relies on electrical capacity to inject ESD discharge current. The larger the capacitance, the better the ESD performance; In high-speed signals, large capacitance can cause signal distortion, while small capacitance has a poor ESD effect. Therefore, MLCC is generally used on power supplies or low-speed signals.

2. For TVS, the anti ESD performance is good, and TVS is generally the most common and commonly used anti ESD device. The interpole capacitance of TVS can be selected to be large, ranging from less than 1 pF to 50-100 pF. Therefore, TVS with small interpole capacitance can be used in high-speed, power, or low-speed circuits. For high-speed signals, TVS with smaller interpole capacitance can be selected, such as TVS with less than 1 pF on USB signals. For power and low-speed signals, TVS with slightly larger interpole capacitance can be selected, such as tens of pF.

3. For ESD suppressors, the internal capacitance is generally below 1pF. Due to the ultra-low electrical capacity of ESD suppressors, the Vave characteristic of ESD suppressors is better than TVS, while the Vpeak characteristic is worse than TVS.

4. For varistors, the price is much lower than TVS, and the ESD resistance performance is worse than TVS. Varistors have less capacitance below 1pF, so their use on high-speed signals is limited. Due to the internal capacitance component, the Vpeak characteristic of varistors is generally better than TVS.

3、 ESD protection device principle

The ESD electrostatic protection diode is connected in parallel to the circuit. When the circuit operates normally, it is in a cutoff state (high resistance state), which does not affect the normal operation of the circuit. When the circuit experiences abnormal overvoltage and reaches its breakdown voltage, it quickly changes from a high resistance state to a low resistance state, providing a low impedance conduction path for the instantaneous current, while clamping the abnormal high voltage within a safe level, thereby protecting the protected IC or line; When the abnormal overvoltage disappears, it returns to the high resistance state and the circuit operates normally.

When the voltage exceeds the conduction voltage of the diode, it is turned on and discharged to ground. Normal signals generally do not reach the conduction voltage and will not reach this voltage, so there will be no ground loss. However, ESD voltage generally exceeds the conduction voltage, which will make the diode turn on. ESD voltage is discharged through ground, without damaging the inside of the instrument.

4、 Function of ESD electrostatic protector

The reason why it is called ESD electrostatic protector is because its function is to provide a protective effect on the circuit when the electronic product equipment is subjected to lightning surge and ESD electrostatic discharge or other transient voltages, so as to protect the electronic product circuit from the damage caused by transient lightning surge and ESD electrostatic.

ESD electrostatic protectors basically absorb and dissipate static electricity, creating a process of charging and discharging to achieve electrostatic protection for electronic equipment. ESD electrostatic impedors in equipment are generally not prone to aging and damage. The operating characteristics of the ESD electrostatic protector are consistent with those of the TVS tube.

5、 Main performance parameters of ESD protection devices

1. Maximum operating voltage

The effective value of the power frequency voltage that is allowed to be continuously applied to both ends of the ESD protection device for a long time. Under this operating state, the ESD device maintains a high resistance state, and this voltage is equal to or greater than the normal operating voltage.

2. Trigger voltage

The starting (conduction) voltage of the ESD element is the highest point of the voltage curve.

3. Clamp voltage

One of the key parameters is the steady-state voltage on ESD components, which is generally read at a specified time (30NS, a concept that many engineers may not understand well). The smaller the value, the smaller the damage caused by electrostatic pulses to the protected device.

4. Leakage current

Under the action of a specified DC operating voltage, the smaller the value of the current flowing through the ESD protection device, the smaller the impact on the protected circuit.

5. Capacitance

One of the key parameters, measured at a given voltage and frequency. The smaller the value, the smaller the impact on the transmission signal, and plays an important role in the normal transmission of data signals. However, it is not to say that the smaller the value, the better. In general, when ESD protection is required for high-frequency signals, a low capacitance value of less than 1PF is required.

The above is a detailed introduction to ESD protection devices. With the increasing number of electronic products, circuit protection is becoming increasingly important. It is necessary to have a sufficient understanding of ESD protection devices!