TLV709: TLV709A50PKR

Hi,

I do not understand your question. Are you referring to the Schottky diode used for reverse current protection for this device? You need a Schottky diode with a low forward drop because you want to make sure the reverse current is flowing through the external diode rather than the parasitic body diode of the pass FET. If the Schottky has a lower forward drop then the body diode, it will activate first.

Sizing the forward current of the Schottky will depend on the nature of the reverse current situation. Are you expecting an indefinite short from VOUT to VIN (which is being tied to GND)? Or is VOUT shorted to VIN which is going high impedance? It can be helpful to try to measure the current in this scenario to determine how big of Schottky you need. If it's a momentary short, you may be able to find an appropriate Schottky diode that can handle the associated surge current. 

In general, you can assume parasitic body diodes to turn on around ~0.6V - 0.7V. Try to find a Schottky with a lower forward voltage across temperature, current and any other relevant conditions

Regards

Ishaan