JAJSEX1A December 2017 – March 2018 TVS1800
If the TVS1800 is in place to protect the device, during a surge event the voltage will rise to the breakdown of the diode at 21 V, and then the TVS1800 will turn on, shunting the surge current to ground. With the low dynamic resistance of the TVS1800, even large amounts of surge current will have minimal impact on the clamping voltage. The dynamic resistance of the TVS1800 is around 30 mΩ, which means 40 A of surge current will cause a voltage raise of 40 A × 30 mΩ = 1.2 V. Because the device turns on at 21.3 V, this means the module input will be exposed to a maximum of 21.3 V + 1.2 V = 22.5 V during surge pulses, well within the LMZ2005 absolute maximum. This pulse is shown in and ensures robust protection of your circuit.
Finally, the small size of the device also improves fault protection by lowering the effect of fault current coupling onto neighboring traces. The small form factor of the TVS1800 allows the device to be placed extremely close to the input connector, lowering the length of the path fault current will take through the system compared to larger protection solutions.