In my design I am using LT4275B POE IC.
How I can set 26V output please can you suggest ?
The LT4275 is a PD Interface with Hotswap Controller. It provides IEEE or LTPoE++ compliant signaling and inrushes the downstream bulk capacitance in a controlled manner. The output voltage is effectively the input voltage. You'll need a DC-DC converter to step down to 26V, or you can use the LT4276 which is a PD Interface with Hotswap and Isolated converter. Check out DC2046A-D for an isolated DC-DC that provides 24V at 1A.