What is ESD electrostatic protector protection?

What is ESD electrostatic protector protection?

Electrostatic discharge, also known as ESD, refers to the charge transfer caused by objects with different electrostatic potentials approaching or directly contacting each other. We start from life. Human hands are prone to losing electrons during drying or friction, resulting in a positive charge on the hands. When a human hand carrying a positive charge contacts an external conductor, the electrons of the conductor will transfer to the human hand, generating an electric current, and the voltage generated during this process can reach thousands of volts. If a hand carrying a positive charge comes into contact with a circuit component, or the USB interface, HDMI interface, etc. on the device, it will generate significant voltage and current at the moment of contact, thereby damaging the circuit component.

But there is a large amount of circuit energy in the commonly used routers, gateways, and other devices. So it is crucial to ensure hardware protection during the production of these devices. Next, let's learn a few ESD related knowledge and understand the mechanism of ESD electrostatic protector protection.

1、 ESD electrostatic protector diode

Firstly, let's take a look at the diodes of ESD electrostatic protectors. The principle of ESD electrostatic protector diode is to connect the ESD electrostatic protector diode in parallel with the circuit. When the circuit works normally, it is in the cut-off state (High impedance), which does not affect the normal operation of the circuit. When the circuit has abnormal overvoltage and reaches its breakdown voltage, it quickly changes from the High impedance to the low resistance state, providing a low impedance conduction path for the instantaneous current, and clamping the abnormal high voltage within a safe level, To protect the protected IC or circuit; When the abnormal overvoltage disappears, it returns to the high resistance state and the circuit works normally.

ESD static diodes, ESD static protectors, ESD protective diodes, etc. are all protective devices. When these appliances protect circuit components, the most critical reference factors are fast response time, low clamping voltage and high surge withstand capacity.

2、 Working principle of ESDdiode

Next, let's understand the working principle of ESD diodes. There is a breakdown voltage in the ESD diode. When ESD occurs, the reverse voltage of the diode exceeds the breakdown voltage, and the diode conducts in reverse, diverting current to ground to protect the circuit; Ideally, when the reverse voltage of the diode is less than the breakdown voltage, the reverse current should be zero.

Of course, in addition to the breakdown voltage. Before selecting an ESD diode, it is necessary to first understand its operating voltage, which is the reverse peak voltage. If the operating voltage of an ESD diode is defined as a current of 10 nanoamperes. So we can understand that this working voltage value is the recommended maximum voltage signal float value. If you choose a diode with a signal range of 0 to 3.6 volts. So you should choose a diode with a Vrwm above 3.6 volts. If the working voltage of the diode you choose is less than 3.6 volts, it is prone to current leakage.

So, when selecting diodes, they should be selected based on the operating voltage.

3、 ESD diode polarity

Next, let's talk about the polarity of the ESD diode. Bidirectional diodes typically have a positive and negative symmetrical I-V curve, operating voltage, and breakdown voltage. This is why bidirectional diodes can support positive and negative signals within their positive and negative operating voltage range. Once a unidirectional ESD diode experiences negative pressure, it will be broken down. Therefore, for unidirectional ESD diodes, ESDit can only support signals in the forward voltage range of 0 to the working voltage. However, the reverse clamping voltage of unidirectional ESD diodes is smaller, which can provide better negative pressure protection.

Both bidirectional and unidirectional ESD diodes can provide positive and negative ESD voltage protection, but bidirectional ESD diodes, due to their symmetrical positive and negative breakdown voltage, can pass through positive and negative signals, while unidirectional ESD diodes can only pass through positive signals. Applicable interfaces such as USB HDMI and some other digital interfaces. However, compared to bidirectional, unidirectional ESD diodes provide better protection against negative pressure