The NMOS pass transistor of the TPS737 provides inherent protection against current flow from the output of the regulator to the input when the gate of the pass transistor is pulled low. To make sure that all charge is removed from the gate of the pass transistor, the EN pin must be driven low before the input voltage is removed. If the EN pin is not driven low, the pass transistor can be left on because of stored charge on the gate.

After the EN pin is driven low, no bias voltage is needed on any pin for reverse current blocking. Reverse current is specified as the current flowing out of the IN pin because of voltage applied on the OUT pin. There is additional current flowing into the OUT pin as a result of the 80-kΩ internal resistor divider to ground (see Figure 6-1 and Figure 6-2).

For the TPS73701, reverse current can flow when V_FB is more than 1.0 V above V_IN.