“ESD means “electrostatic discharge”. ESD is a discipline that studies the generation, harm, and protection of static electricity. Therefore, it is customary in the world to refer to the equipment used for electrostatic protection as ESD, and the Chinese name is electrostatic resistance.
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First of all, we need to know what is ESD?
ESD means “electrostatic discharge”. ESD is a discipline that studies the generation, harm, and protection of static electricity. Therefore, it is customary in the world to refer to the equipment used for electrostatic protection as ESD, and the Chinese name is electrostatic resistance.
Secondly, we need to understand what are the hazards of static electricity in the circuit board?
1) Static electricity is easy to attract fine dust and cause certain pollution
2) Electrostatic discharge will cause device breakdown. Electrostatic discharge is a process of charge accumulation. When the charge accumulates to a certain extent, when a device approaches it, the electrostatic discharge will cause certain damage to the device, thereby reducing the device’s performance. reliability
3) Static electricity will cause electronic interference, because a lot of radio waves are radiated when electrostatic discharge, these waves are all with frequency, which affects the normal operation of surrounding devices
So, we usually do a good job of electrostatic protection in the circuit?
The picture above is the most common protection circuit for handling static electricity in our circuit. Add esd to the interface device for grounding.
1) When our system is not disturbed, the circuit works normally, and the ESD device can be ignored and almost does not work
2) When the external interface voltage exceeds the breakdown voltage (VBR) of the ESD device, the ESD device starts to function and shunts the current to the ground.
For ESD, how should we make a selection?
ESD is mainly divided into four categories: TVS diode, varistor, MLCC, ESD suppressor. The application scenarios of each device are also different. The most commonly used ESD device is the tvs diode.
1) Working voltage,
When choosing an ESD device, you should choose a system whose working voltage is less than the working voltage (VRWM) of the ESD device. For example, if the system is 0~5V, then we should choose a TVS with a working voltage (VRWM) greater than 5V.
2) Signal type
The choice of unidirectional ESD devices and bidirectional ESD devices. Bidirectional ESD devices can pass positive and negative breakdown voltage (VBR) signals, while unidirectional ESD devices can only pass positive breakdown voltage (VBR) signals. Will cause ESD device breakdown.
3) Parasitic capacitance
ESD devices have parasitic capacitance, as shown in the figure is the influence of parasitic capacitance on high-speed circuit interfaces. Parasitic capacitance will affect the rise and fall speed of the level, and affect the output signal.
4) According to the maximum withstand voltage impact of the circuit system, select the appropriate clamping voltage;
5) Ensure that ESD devices can meet or exceed IEC 61000-4-2 level 4.
First of all, we need to know what is ESD?
ESD means “electrostatic discharge”. ESD is a discipline that studies the generation, harm, and protection of static electricity. Therefore, it is customary in the world to refer to the equipment used for electrostatic protection as ESD, and the Chinese name is electrostatic resistance.
Secondly, we need to understand what are the hazards of static electricity in the circuit board?
1) Static electricity is easy to attract fine dust and cause certain pollution
2) Electrostatic discharge will cause device breakdown. Electrostatic discharge is a process of charge accumulation. When the charge accumulates to a certain extent, when a device approaches it, the electrostatic discharge will cause certain damage to the device, thereby reducing the device’s performance. reliability
3) Static electricity will cause electronic interference, because a lot of radio waves are radiated when electrostatic discharge, these waves are all with frequency, which affects the normal operation of surrounding devices
So, we usually do a good job of electrostatic protection in the circuit?
The picture above is the most common protection circuit for handling static electricity in our circuit. Add esd to the interface device for grounding.
1) When our system is not disturbed, the circuit works normally, and the ESD device can be ignored and almost does not work
2) When the external interface voltage exceeds the breakdown voltage (VBR) of the ESD device, the ESD device starts to function and shunts the current to the ground.
For ESD, how should we make a selection?
ESD is mainly divided into four categories: TVS diode, varistor, MLCC, ESD suppressor. The application scenarios of each device are also different. The most commonly used ESD device is the tvs diode.
1) Working voltage,
When choosing an ESD device, you should choose a system whose working voltage is less than the working voltage (VRWM) of the ESD device. For example, if the system is 0~5V, then we should choose a TVS with a working voltage (VRWM) greater than 5V.
2) Signal type
The choice of unidirectional ESD devices and bidirectional ESD devices. Bidirectional ESD devices can pass positive and negative breakdown voltage (VBR) signals, while unidirectional ESD devices can only pass positive breakdown voltage (VBR) signals. Will cause ESD device breakdown.
3) Parasitic capacitance
ESD devices have parasitic capacitance, as shown in the figure is the influence of parasitic capacitance on high-speed circuit interfaces. Parasitic capacitance will affect the rise and fall speed of the level, and affect the output signal.
4) According to the maximum withstand voltage impact of the circuit system, select the appropriate clamping voltage;
5) Ensure that ESD devices can meet or exceed IEC 61000-4-2 level 4.