MSP430FR2476: ADC measurement in LPM3 for lowest power consumption

Example msp430fr267x_ADC12_11.c demonstrates the main principles.

https://dev.ti.com/tirex/explore/node?node=A__AE6ZjPGFNmcL5vCm9P2MCQ__msp430ware__IOGqZri__LATEST

It uses LPM0 but (based on inspection) I'm pretty sure it will run in LPM3. It also expects a 32kHz crystal (LFXT) but the REFOCLK would be a suitable substitute.

The notions:

1) Trigger from a timer clocked by ACLK (active in LPM3).

2) Clock the ADC with MODCLK (ADCSSEL=0), so it finishes quickly. (MODCLK is powered only when needed.) 

3) The Example sets INTREFEN=1, which runs the internal reference all the time, at a cost of about 20uA. This is debatable: If you set (leave) INTREFEN=0 but ADCMCTL uses it, it will start/stop the reference for each conversion, causing a delay of about 30us [Ref User Guide (SLAU445I) Sec 21.2.3]. If your sampling is fairly slow, this will probably not be noticeable.

4) CONSEQ=2 with MSC=0, so you don't have to fiddle with ENC.

These are general principles. Specifics of your use case may affect things. (Multiple channels? Very fast/very slow sampling? Very high impedance source?)

[Edit: Forgot about CONSEQ.]