I am trying to read an input voltage in the .3-2V or so range with a higher precision than that offered by the ADC12 module. I am trying to use the SD16 on the MSP430FE4242, but I have some questions about it.
It appears that the input voltage range is limited to +- Vref/2, this means that I have to shift my input voltage range to this range using some kind of opamp circuit. Is there any simpler way around this? Does anyone have a simple opamp circuit to suggest?
In the MSP430x4xx users guide it says "An external voltage reference can be applied to the VREF input when SD16REFON and SD16VMIDON are both reset.". I would expect that when I use an external reference larger than the 1.5 V max listed on the datasheet it would set itself to the max range, or something like that, but when I try it appears to continue using 1.2 V as the reference (when I input .63 V it maxes out the ADC reading at 65520). So there is no way to get a larger voltage swing?