My expectation may be wrong, but I am trying to use an external Vref value to modify the range of output values produced by the DAC module. I’m using a PIC16F1503 with Vdd = 5V so voltage increments are around 0.16V through the range 0-5V when I use Vdd as the reference for DAC. I am trying to get a finer granularity in the voltage levels by using an external 2.5V reference and was expecting to get voltage increments of around 0.08V between 0 and 2.5V.
However, when I provide the 2.5V input, I still see the increments and range associated with the 5V Vdd reference.