To select the ideal ESD protection solution for a given application, we must understand both the system that needs protection, as well as the properties of protection devices. The ESD device must not disturb the functionality of the system it is protecting, and also must react quickly to shunt dangerous current and voltage spikes to ground during surge and ESD events.
Reverse Working Voltage – VRWM: Maximum nominal working voltage at which the device is intended for use. At this voltage, the ESD diode will appear in the "off" state as a high impedance element that will have very low leakage current.
Forward Voltage – VF: Voltage in the forward direction at the test current IF.
Reverse Breakdown Voltage – VBR: At this voltage, the ESD diode starts to conduct, or turn "on". The breakdown is measured at a test current, IT, typically from 1mA to 10 mA. VBR is specified as a minimum value for ESD applications and usually is 10% to 15% above the VRWM. When selecting an ESD protection diode a designer must ensure that this voltage is higher than the maximum working voltage of the system it is protecting.
Capacitance – C: Capacitance is a parameter that becomes a concern for applications that operate at high data rates. High capacitance will degrade signals, compromising high speed applications. Low capacitance devices are preferred for high speed applications such as HDMI and USB connections.