It has also the FVR (Fixed Voltage Reference) and the datasheet claimed that the ADC can be connected to the FVR.
But, I don't see a connection to it. There is no mentions of these at all in the ADC section. Suddenly, the mentions of connecting the FVR to the ADC disappeared in the respective section. It seems that there is a printing error.
Workarounds:
1.) So if you need to have a FVR on the little thing, too bad, it doesn't have it. There is a DAC though, you can tune it to whatever voltage you want and then feed it back to the positive Vref pin. However, you need an Op-Amp and wire it as a buffer between the Vref and the DAC output.
2.) If you need to reduce part count (or cost), use a voltage divider using resistors. Or with a potentiometer. Thing is, cover them with a candle wax after you tune it so that you won't get wrong readings.
3.) Use an external digital potentiometer (the microcontroller has a hardware SPI/I2C) and tune the thing and connect the output back to the Vref pin. This is the most expensive one but it did the job properly.
The ones with the FVR are the PIC16F18xx ones. Lowest end of these are 2x more expensive than the PIC16F1503.
Still the PIC16F1503 has other good stuff inside, so when there's no FVR to the ADC, doesn't mean that it is the end of the world!
