DC/DC Converter Application Note
The Shutdown Function
Due to the typical step-up DC/DC converter circuit, a voltage may appear at the output of the circuit even if the driver IC is in the standby mode. A current flows from the battery, through the inductor and diode to the output pins. In case an OLED display is connected, it is powered constantly and it may have an impact to the lifetime of the OLED. In addition, when the input voltage is close to the Vf voltage of a white LED, it is unable to turn these off properly.
The R120xx Series have an internal NPN transistor instead of a diode. In standby mode, the NPN transistor turns off and isolates the current flow from input to output.
The R1213K Series is able to shutdown that controls an external P-channel MOSFET by FLAG pin.