3 Key electrical characteristics of TVS diodes (ESD protection diodes)

Key characteristics for normal operation (in the absence of an ESD event)
Since an ESD protection diode is connected in the reverse direction, the voltage across it is lower than the reverse breakdown voltage (V_BR) during normal operation. Therefore, the ESD protection diode does not conduct during normal operation. At this time, a depletion layer is formed across the pn junction, causing the diode to act as a capacitor. The following three considerations apply to normal operation when selecting ESD protection diodes:

3-1-1  Whether the reverse breakdown voltage (V_BR) of an ESD protection diode is sufficiently higher than the amplitude (maximum voltage) of the signal line to be protected
3-1-2  Whether the total capacitance (C_T) of an ESD protection diode is sufficiently low with respect to the frequency of the signal line to be protected
3-1-3  Signal polarity (i.e., whether the signal voltage crosses the GND potential like an analog signal)

Key characteristics for protection against ESD events
When an ESD is introduced into a system, ESD protection diodes either conduct or enter reverse breakdown. A unidirectional ESD protection diode absorbs ESD energy by entering reverse breakdown in the event of a positive ESD strike and by going into conduction in the event of a negative ESD strike. There are three points to note to prevent the DUP from being destroyed by an ESD pulse:

3-2-1  Low dynamic resistance (R_DYN)
3-2-2  Low clamp voltage (V_C) and first peak voltage
3-2-3  Operations of an ESD protection diode to absorb ESD pulses with different polarities