9.2.2 Detailed Design Procedure

If the TVS2701 is in place to protect the device, the voltage will rise to the breakdown of the diode at 32 V during a surge event. The TVS2701 will then turn on to shunt the surge current to ground. With the low dynamic resistance of the TVS2701, even large amounts of surge current will have minimal impact on the clamping voltage. The dynamic resistance of the TVS2701 is around 40 mΩ, which means a 25-A surge current will cause a voltage raise of 25 A × 40 mΩ = 1 V. Because the device turns on at 32 V, this means the module input will be exposed to a maximum of 32 V + 1 V = 33 V during surge pulses, well within the MUX36D04 absolute maximum.

In addition, because the TVS2701 is a bidirectional device it is designed to withstand reverse wiring conditions. When the supplies is wired backwards, it applies –27 V to the V_INPUT relative to ground, which does not break down the TVS diode, and does not damage the input to the MUX36D04 because of the reverse current protection diode. If a unidirectional diode like the TVS2700 were used in this case, the –27 V would cause the diode to shunt current until it overheat and breaks.

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 TVS2701 allows the device to be placed extremely close to the input connector, which lowers the length of the path fault current going through the system compared to larger protection solutions.