7 Electrical characteristics of TVS diodes (ESD protection diodes)

Electrical characteristics

Working peak reverse voltage, V_RWM
At a voltage lower than the working peak reverse voltage, an ESD protection diode exhibits a very high impedance. (Even if the working peak reverse voltage is applied, only a current less than the specified leakage current flows.) The designer can use this parameter as a guide to ensure that it is above the maximum operating voltage of the signal line to be protected.

Total capacitance, C_t
C_T is the equivalent capacitance across a diode’s terminals when a small signal is applied at the specified reverse voltage and frequency. The total capacitance is the sum of the junction capacitance of a diode and the parasitic capacitance of its package. Junction capacitance decreases as reverse voltage increases.

Dynamic resistance, R_DYN
The dynamic resistance is the current slope of the V_F–I_F curve between V_BR and V_C when an ESD protection diode goes into reverse breakdown as reverse voltage is increased. The dynamic resistance and the clamp voltage described below represent the ESD performance of an ESD protection diode.

Reverse breakdown voltage, V_BR
Reverse breakdown voltage is the voltage at which an ESD protection diode begins to conduct the specified amount of current under specified conditions (defined typically at 1 mA, although this differs from device to device). V_BR is originally a parameter defined for Zener diodes. V_BR is defined as the voltage at which an ESD protection diode turns on.

Reverse current, I_R
Reverse current is the leakage current that flows in the reverse direction when an ESD protection diode is reverse-biased at the specified voltage. In the case of ESD protection diodes, I_R is defined at the working peak reverse voltage (V_RWM).

Clamp voltage, V_C
Clamp voltage is the maximum voltage to which an ESD protection diode is clamped when exposed to the specified peak pulse current. V_C is generally measured at multiple peak pulse current points. As shown in Section 6 (Figure 6.1), an 8/20 μs waveform is used for the peak pulse current. The dynamic resistance and the clamp voltage represent the ESD performance of an ESD protection diode.