My goal is to suppress transient voltage spikes from damaging the 5V, 600mA Step-Down Voltage Regulator D36V6F5. I believe the transients are a result of high inductance in the wires between the power supply and the circuit.
There are a couple of solutions listed in Pololu's guide to transients, but only adding a series resistor or a large electrolytic cap is possible in my case.
The resistor would result in power loss and a cap is just physically very large.
So my idea was to use a TVS diode -- SMF48A-TP. Now ignoring the fact that the maximum breakdown voltage Vbr is 58.9V, which is already too much for the D36V6F5, whose limit is 50V, I'm still seeing spikes of up to 65V.
Why is that?
I don't have the circuit for the D36V6F5, but I do know that it has 5.3 uF and 100 nF capacitors on the input.