As an example, the figure (Definitions of Electrical Characteristics) contained in the datasheet of a unidirectional TVS diode are given below. Although a TVS diode has many voltage and current specifications, attention should be paid to the working peak reverse voltage (VRWM) here.
VRWM is a threshold below which the TVS diode remains off when Ta=25°C. It is necessary to select TVS diodes with a VRWM higher than the maximum voltage of the signal lines to be protected.
However, TVS diodes with an excessively high VRWM (i.e., high clamp voltage) cause more energy to flow into the device under protection in the event of ESD. Select the optimum TVS diodes according to the design specifications.