What's the maximum voltage that can be given to VREF pin of TL1431AIYDT (through voltage divider from output) ???

[PS.17]

Hii... I'm using TL1431AIYDT to get 5V reference supply ( (+/-)20mV tolerance). My input voltage is 6V. We need to protect the IC from Short To Battery (7V to 18V) (at the output). We are planning to use a schottky to protect from STB. During STB (18V), the VREF pin rises to 9V (50% due to voltage divider). What's the maximum voltage that can be given to VREF pin of TL1431AIYDT ??? Attaching the simulation pic for your reference.

[PS.17]

This voltage reference part is very critical in our design. Quick replies are appreciated.. Thanks in advance... :)