I was looking at the data sheet of a common 12v relay and noticed it mentioned using a resistor instead of a flyback diode for circuit protection.
On the last page for 12V models it reads;
When connecting a coil surge protection circuit to these relays, we recommend a zener diode with a zener voltage of 24 V or higher, or a resistor (680Ω to 1,000Ω). When a diode is connected to the coil in parallel, the release time will slow down and working life may shorten. Before use, please check the circuit and verify that the diode is not connected in parallel to the coil drive circuit.
My question is how does a resistor in parallel with a coil prevent induced voltage from reaching the rest of the circuit? If we considered the coil to be a high voltage source for a moment, won't that voltage potential reach anything in parallel with it?
Or, is the resistor connected from the coil drive circuit to ground? In either case - how is the math calculated for the resistor value required?