We can estimate the input impedance.
The MAX14626 is in normal mode (loop current is < 25mA):
Zin=(Vdrop/Iloop + R LOAD ) ||(Vin/I Q ), where R LOAD (typ)= 250 Ohm, I Q = 56uA (max), Vdrop = 2.8V @ Iloop = 24mA.
That gives us an estimate of ~300 Ohm to 370 Ohm (max).
The MAX14626 is in protection mode (loop current is ~30mA):
Zin = Vin/30mA for a positive surge
Zin = Vin/0.3uA for a negative surge
where Vin is TVS clamping voltage