ESD Protection Diode Basics: Working and Vendors

This page explains the function of an ESD (Electrostatic Discharge) protection diode. We’ll cover the basics of how these diodes work, their key characteristics, and list some of the vendors that supply them.

Figure 1: ESD diode symbols

ESD diodes are crucial components in protecting sensitive electronic circuits from damage caused by sudden electrostatic discharges.

Figure 2: ESD diode DC characteristic

Figure 2 illustrates the DC characteristic of an ESD diode. Notice the similarity to a Zener diode, particularly the voltage snapback behavior, which is key to its ESD protection function.

ESD Diode Operation

ESD diodes are designed with the following characteristics:

• High Avalanche Voltage: Allows the diode to withstand high voltage spikes during an ESD event.
• Low Leakage Current: Minimizes current flow under normal operating conditions.
• Low Capacitance: Prevents signal attenuation, ensuring signal integrity.

Under normal operating conditions, the ESD diode behaves like a standard Zener diode, exhibiting a small leakage current. However, when the voltage exceeds a specific trigger value (the avalanche voltage), the diode’s characteristic snaps back. This snapback effect allows the diode to conduct a large amount of current while maintaining a relatively low voltage, effectively clamping the voltage and protecting the downstream circuitry.

The ESD diode remains in this “snapback mode” as long as a minimum current (holding current) or voltage (holding voltage) is maintained. When the voltage or current drops below these holding values, the diode abruptly returns to its normal mode, conducting only a very small leakage current. This fast switching action is essential for quickly diverting ESD strikes.

ESD Protection Diode Vendors

Here are some of the major vendors that offer ESD protection diodes:

• Infineon
• ON Semiconductor
• TI (Texas Instruments)
• Vishay
• Littelfuse