MCU PIN Open Drain Protection
Do note that the wording is actually pretty strange. If the fan is acting as an input, I don't see any reason why the fan would drive the line to 5V and endagnger the 3.3V pin on the MCU. The fan pin might require 5V to respond but that is different than the fan applying 5V to its input line (which doesn't make too much sense) and damaging the MCU. You might be able to just drive the fan directly without concern as long as the fan responds to 3.3V logic thresholds. I think it should say the fan can only be driven to a maximum of 5V.


  
    This signal SHALL be pulled up to a maximum of 5.25V within the fan. 
  


But there is a chance that the fan is expecting the driver to be open-drain, and if so then the pull-up resistor may have been integrated into the fan itself so the external circuit does not need one. In that case you need the circuit below.







simulate this circuit &ndash; Schematic created using CircuitLab

If the fan is not open-drain input but requires 5V logic thresholds then you need to use a 3.3V to 5V push-pull level translator.