Is it possible to use the above construction to adapt a 3,3V signal to a level acceptable for 2,5V FPGA Vccaux input ..? And thus eliminate or significantly reduce the need for a shunt resistor as mentioned in XAPP453 page 5 "Managing Reverse Current" ..?
Maybe one could use R=1000 ohm to further reduce the reverse current. As (3.3-2.5-Vf)/I_leak = 8000 ohm. I_leak = 0.000025 Amp (ds099.pdf p58).
The original idea was to not need any resistor at but as a component with a suitable Vf seems hard to find. I thought this solution will at least reduce the problem.