9.2.2 Detailed Design Procedure

If the TVS0701 is in place to protect the device, the voltage will rise to the breakdown of the diode at 10 V during a surge event. The TVS0701 will then turn on to shunt the surge current to ground. With the low dynamic resistance of the TVS0701, large amounts of surge current will have minimal impact on the clamping voltage. The Specifications section guarantees absolute maximum clamping of 12.9 V during surge pulses, so there is no risk of the input to the TPS77033 about the absolute maximum of 13.5 V. This is well within the absolute maximum input voltage to ensure robust protection of the circuit.

In addition, the TVS0701 provides protection against reverse voltage application that could accidentally be caused by shorts between pins. If –7 V is applied to the V_IN pin, the TPS77033 will not be harmed because the series diode will prevent the voltage from being applied to the input, and the TVS0701 will not shunt current because the reverse working voltage is –7 V. If the TVS0500 or a unidirectional device is used in this case, a –7-V short would cause the device to shunt current until it fails.

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 TVS0701 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.

Finally, the low leakage of the TVS0701 will have low input power losses. At 7 V, the device will see typical 0.25-nA leakage for a constant power dissipation of less than 1 nW, a negligible quantity that will not effect overall efficiency metrics or add heating concerns.