2. Rating of C 6 1000-4-2: TVS diode supplier determines this parameter value by increasing ESD voltage until the diode fails. The fault point describes the robustness of the diode. The higher the value of this parameter, the better. More and more Littelfuse TVS diodes can reach the contact discharge voltage of 20 kV or even 30 kV, far exceeding the highest level specified in IEC 6 1000-4-2 (the contact discharge voltage of level 4 is 8 kV, as shown in Figure 2).