SLAU846B June 2023 – November 2024 MSPM0G1105 , MSPM0G1106 , MSPM0G1107 , MSPM0G1505 , MSPM0G1506 , MSPM0G1507 , MSPM0G1519 , MSPM0G3105 , MSPM0G3105-Q1 , MSPM0G3106 , MSPM0G3106-Q1 , MSPM0G3107 , MSPM0G3107-Q1 , MSPM0G3505 , MSPM0G3505-Q1 , MSPM0G3506 , MSPM0G3506-Q1 , MSPM0G3507 , MSPM0G3507-Q1 , MSPM0G3519
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 noninverting input needs to be biased up to ensure that the output stays within the linear range. The noninverting input can be sourced from the external OPAx_INx+ input or from a DAC input.
Figure 14-5 shows an example of the OPA inverting PGA mode with the 8-bit reference DAC as bias cancellation.