My objective is to remove my current ADC and use the MSP430 ADC instead because I already have it on my board. It will be setup to measure thermistor in bridge configuration. I'm thinking to set it up so that DVCC is used as the reference since based on the specification the gain error is 2 LSB this way versus 3% when internal ref is used. The bridge will also be powered by DVCC from the same LDO and this should eliminate error due to DVCC variation. Is my understanding correct that using DVCC as reference on this device resulted in better gain error?
The ADC on this MSP430 has better gain than my previous ADC but not the offset (1LSB vs 6.5mV or ~2 LSBs on the MSP430). Thus making high temperature (lower thermistor voltage) conversion worse. I've read TI's application note "Designing With the MSP430FR4xx and MSP430FR2xx ADC", and in the note Chapter 5 it wrote that the ADC gain and offset can be improved to 0.5 LSB respectively by calibrating it using the TLV. However, the title of this chapter is a little confusing to me because it appear to me it referring to only the VREF and the Internal Temperature sensor. I hope that maybe TI could clarify if I will see the same improvement if I calibrate it for my thermistor measurement?
I also won't be able to buffer the signal to the ADC, do you foresee any problem with this?
Besides that, I also have some other question on the ADC specs that I hope TI can help me with.
1. is the TLV calibration cover for entire operating temperature?
2. I saw there is two address each for gain and offset in the TLV table. Do I have to combine the two values together to form the correct calibration constant? (E.g 1A16h and 1A17h for gain factor..)
3. If in case I have to use the internal reference for conversion, will the gain error also be improved from 3% to 0.5 LSB after calibration?
4. The appnote I mentioned earlier stated that the gain/error improvement is only at room temp. What are the error when operating outside of room temp? What's the gain/error drift error?
