I have found one discussion regarding using dual 3.3V supplies for VDDA and VREFH and disussing whether or not this was a good idea. I have searched, but couldn't find anything on this subject.
My device: MK22FN256VLL12
I need to use a 2.5V external, high precision voltage reference for the ADC, so that is connected at the VREFH pin.
However, I also want to ensure the the performance/gain/offset of the ADC is as good as possible, so I am implementing the calibration procedure as also described in AN3949.
AN3949 states that VREFH and VDDA should be above 3V. The Reference manual for my device states that VREFH = VDDA. I meet neither of those requirements.
- What would your recommendation be in such a case?
- Can I just multiply the sum of CLP and CLM registers by 3.3/2.5 or something?
I'd rather not spend money on a DC switch that can be controlled by a GPIO, if this can be avoided.