The output of the FVR, which is connected to the ADC, is routed through an independent programmable gain amplifier. This amplifier can be programmed for a gain of 1x, 2x or 4x, to produce the three possible voltage levels.
The ADFVR bits are used to enable and configure the gain amplifier settings for the reference supplied to the ADC module.
Refer to the figure below for the block diagram of the FVR module.
Figure 1. FVR Block Diagram
