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DAC12 Operation
23-8 DAC12
23.2.5 DAC12 Output Amplifier Offset Calibration
The offset voltage of the DAC12 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 DAC12
digital input produces a sufficient positive output voltage to overcome the
negative offset voltage, resulting in the transfer function shown in Figure 23−5.
Figure 23−5. Negative Offset
Output Voltage
0
DAC Data
Negative Offset
When the output amplifier has a positive offset, a digital input of zero does not
result in a zero output voltage. The DAC12 output voltage reaches the
maximum output level before the DAC12 data reaches the maximum code.
This is shown in Figure 23−6.
Figure 23−6. Positive Offset
V
cc
Output Voltage
0
DAC Data
Full-Scale Code
The DAC12 has the capability to calibrate the offset voltage of the output
amplifier. Setting the DAC12CALON bit initiates the offset calibration. The
calibration should complete before using the DAC12. When the calibration is
complete, the DAC12CALON bit is automatically reset. The DAC12AMPx bits
should be configured before calibration. For best calibration results, port and
CPU activity should be minimized during calibration.