Working Principle

3.1 Normal Operation

Under normal operating conditions, when the voltage across theElectrostatic Discharge (ESD) Protection Diodes protection diode is within the normal range (lower than the breakdown voltage), the diode behaves like an open circuit. It has a very high resistance, and only a negligible leakage current flows through it. This ensures that the diode does not interfere with the normal operation of the electronic circuit it is protecting. For example, in a typical 5V - powered circuit, if the ESD diode has a breakdown voltage of 8V, it will not conduct during normal operation and will have no impact on the circuit's electrical characteristics.

3.2 ESD Event Response

When an Electrostatic Discharge (ESD) Protection Diodes event occurs and the voltage across the diode exceeds its breakdown voltage (also known as the trigger voltage), the ESD protection diode enters the avalanche breakdown or Zener breakdown region, depending on its design. In the avalanche breakdown mode, the high - voltage ESD pulse causes electrons in the semiconductor material to gain enough energy to collide with other atoms, knocking out additional electrons. This creates a chain reaction, resulting in a rapid increase in the number of charge carriers and a significant decrease in the resistance of the diode. In Zener breakdown, the strong electric field at the PN - junction directly pulls electrons from the valence band to the conduction band, allowing a large current to flow.

Once the diode breaks down, it can conduct a large amount of Electrostatic Discharge (ESD) Protection Diodes current to the ground, diverting the potentially damaging ESD energy away from the sensitive electronic components. For example, if an ESD event generates a 20kV voltage spike, the ESD protection diode will break down and quickly conduct the current, reducing the voltage across the protected component to a safe level. The diode remains in the conducting state as long as the ESD current persists, and once the ESD event subsides and the voltage drops below the holding voltage (a value slightly lower than the breakdown voltage), the diode returns to its high - resistance state, ready to protect against future Electrostatic Discharge (ESD) Protection Diodes  events.