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
The offset voltage of the DAC output amplifier can be positive or negative. When the offset is negative, the output amplifier attempts to drive the voltage negative but cannot do so. The output voltage remains at zero until the DAC digital input produces a sufficient positive output voltage to overcome the negative offset voltage, resulting in the transfer function in Figure 16-6.
When the output amplifier has a positive offset, a digital input of zero does not result in a zero output voltage. The DAC output voltage reaches the maximum output level before the DAC data reaches the maximum code (see Figure 16-7).
The DAC can self-calibrate the offset voltage of the output amplifier. The application can perform self-calibration of the DAC output buffer to achieve the offset error given in the electrical specification. The CALCTL.CALON bit is used to initiate the offset error calibration. The DAC output is high impedance while the calibration is active. When the calibration is complete, the CALCTL.CALON bit is automatically reset. Software must configure the CTL1.AMP bits before calibration.
For best calibration results, activity on the device pins and in the CPU must be minimized during calibration. Calibration data is loaded into CALDATA; when DAC self-calibration is initiated using the CALCTL.CALON bit, the CALDATA register is continuously updated during the course of calibration. Read the CALDATA register only after the CALCTL.CALON bit is cleared, otherwise incorrect values can be read. The DAC calibration data format is twos complement. Only the lowest byte is used and the upper bytes have no effect on the offset calibration.
Recalibrate the DAC output buffer after changing the reference voltage level in the VREF module when DAC is in use.