I have a new design using an MKL03Z32CAF controller. I want to use the internal bandgap voltage reference to calibrate my A2D against a Vdd that will fall as the CR2032 battery discharges. I had assumed that I could use the bandgap Vref internally but it now seems that I may have to assign VrefOut to one of the pins and connect a capacitor to that pin.
1. Is the external VrefOut pin - with capacitor connected - essential to the use of the internal bandgap Vref?
2. Are there other ways to get accurate A2D readings given that my Vdd (used as Vref) could vary between 3.2 and 2.6 volts?