The TPS709 has the following functional modes:

1. Enabled: When the enable pin (EN) goes above 0.9 V, the device is enabled. EN is pulled high by a 300-nA current source; therefore, EN can be left floating to enable the device. Do not connect EN to VIN. The EN pin is clamped by a 6.5-V Zener diode. Do not exceed the 7-V absolute maximum rating on the enable pin or excessive current flowing into the Zener clamp will destroy the device.
2. Disabled: When EN goes below 0.4 V, the device is disabled. During this time, OUT is high impedance and the current into IN (I_(SHUTDOWN)) is typically 150 nA.