9.2.2 Detailed Design Procedure

If the TVS2201 is in place to protect the device, the voltage will rise to the breakdown of the diode at 26.6 V, during a surge event. The TVS2201 will then turn on to shunt the surge current to ground. With the low dynamic resistance of the TVS2201, even large amounts of surge current will have minimal impact on the clamping voltage. The dynamic resistance of the TVS2201 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 26.6 V, this means the input will be exposed to a maximum of 26.6 V + 1 V = 27.6 V during surge pulses, robustly protecting the USB Type-C port.

In addition, the TVS2201 provides protection against reverse voltage application that could accidentally be caused by shorts between pins. If –20 V is applied to the VBUS pin, the TPS65982 will not be harmed because the series diode will prevent the voltage from being applied to the input, and the TVS2201 will not shunt current because the reverse working voltage is –22 V. If the TVS2200 or a unidirectional device is used in this case, a –20-V short would cause the device to shunt current until it fails.

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 TVS2201 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.