We have a a project where there a system powered by 13s Li battery - 54.6V max voltage of pack. The buck regulator we're choosing for this has an absolute max of 76V. For this we're considering two TVS diodes
824521481 Vbr=56.1V Vcl=77.4V
SMBJ48CD-M3/H Vbr=54.1V Vcl=76.3V
In the first option quite small current will flow through the TVS, but max clamping voltage is greater than 76V rating of buck regulator. In second case there is a possibility of more than 1 mA current flowing through diode when battery is fully charged but clamping voltage is much closer to max rating of buck regulator.
Which of the two options is better? Or will both of them not work and we've to look at a higher voltage rating for the buck?
Edit 1 for more context: This is a small add-on circuit with 2G GSM modem (2A peak) being powered from the battery of an EV that has a motor size of 0.5 to 2kW and battery capacity of 4 to 8 kWh. So at 48V from battery during the GSM peak current also there is sub 300 mA current draw. We are looking at protecting the circuit from any transients or surges from the motor operation, charger connection or BMS battery cut-off during any fault. We are not yet sure of what kind of transients to expect in such a system.