SLAU846A June 2023 – October 2023 MSPM0G1105 , MSPM0G1106 , MSPM0G1107 , MSPM0G1505 , MSPM0G1506 , MSPM0G1507 , MSPM0G3105 , MSPM0G3105-Q1 , MSPM0G3106 , MSPM0G3106-Q1 , MSPM0G3107 , MSPM0G3107-Q1 , MSPM0G3505 , MSPM0G3505-Q1 , MSPM0G3506 , MSPM0G3506-Q1 , MSPM0G3507 , MSPM0G3507-Q1
In this mode, the inverting input is sourced from the external OPAx_IN1- crossing the resistor ladder of the PGA. The MSEL bits select OPAx_IN1- as the source (MSEL = 0x1) and the NSEL bits must select the RTAP as the inverting input for the amplifier (NSEL = 0x4). Because the OPA is a single supply amplifier, the non-inverting input needs to be biased up to ensure that the output stays within the linear range. The non-inverting input can be sourced from the external OPAx_INx+ input or from a DAC input.
Figure 12-5 shows an example of the OPA inverting PGA mode with the 8-bit reference DAC as bias cancellation.