THVD1500: ESD Protection Issue

Part Number:THVD1500

Hi  Experts: 

             I have one question for the ESD protection on the THVD1500 ,  as the description of the spec in the datasheet , the value of the Vesd is the voltage with respect to the ground (common mode ) , with this spec, perhaps we don't need to add the external TVS diode between A,B terminal and ground. 

             However, I don't know the ESD strength value between A,B terminals so that i can't judge if need to add the TVS diode between the A,B terminal.