UV sensor ML8511

[Gusse]

It seems that it is challenging to calculate accurate UV-Index (0-11+), as you would like to do.
Index is weighted using 3 different wavelengths and this broadband UV sensor covers all of them.
Problem is that there is just one output value for all of them.

Wavelenghts and weighting:
295 nm -> 1x , 305 nm -> 0.22x , and 325 nm -> 0.003x
How is the UV-Index Calculated?

Basically you could generate your own multiplier, based on above values and hands-on testing.

About operating voltages, even there is 3.3v LDO for chips itself, EN (enable pin) still need to be in spec. Put voltage divider between PIC and sensor.
ADC is not a problem, measure & scale result (1v -> 0, 3v -> 1023, 10-bit ADC)