The enable pin (EN) is active high and compatible with standard TTL-CMOS levels. V_EN below 0.5 V (maximum) turns the regulator off and drops the GND pin current to approximately 10 nA. When EN is used to shutdown the regulator, all charge is removed from the pass transistor gate. A V_IN above 1.7 V (minimum) turns the regulator on and the output ramps back up to a regulated V_OUT (see Figure 5-39).

When shutdown capability is not required, EN can be connected to V_IN. However, the pass transistor can possibly not be discharged using this configuration, and the pass transistor can be left on (enhanced) for a significant time after V_IN is removed. This scenario can result in reverse current flow (if the IN pin is low impedance) and faster ramp times upon power up. In addition, for V_IN ramp times slower than a few milliseconds, the output can overshoot upon power up.

Current limit foldback can prevent device start-up under some conditions. See the Internal Current Limit section for more information.