Data Sheet

NAU7802 24-bit ADC
Nuvoton Confidential - 21 - Revision 1.7
At all times, when reading a value from the ADC registers, the gain and offset calibration
values are added/subtracted to the ADC value before being output. The default values for the
calibration registers is zero, so these have no affect on the ADC output value until after a
calibration operation has been instantiated.
The resulting output value is calculated as:
ADC Output Value = Gain_Calibration* (ADC measurement - Offset_Calibration)
8.6.2 Calibration Limitations
Note that the offset that is trimmed from the input is mapped through the gain register.
Additionally:
 Calibration can be limited by signal headroom in the analog path
 With the converters intrinsic gain & offset error the minimal full scale input range may be higher
or lower.
8.6.3 Calibration Error
A calibration error may occur during gain calibration when one of the following happens:
 The gain required to map input to full scale is larger than the range available in the gain register
~ 256
 The offset adjusted input is negative, e.g. 256 > gain > 0
If there is a calibration error, CAL_ERR will set to Logic=1 when the calibration sequence is
completed. Once CAL_ERR is set to Logic=1, it will remain in this state until either the
NAU7802 is reset, or after a valid calibration sequence is completed.
When CAL_ERR = 1, the data in the calibration registers is invalid. It is recommended
perform the calibration routine again, or to write a default value into the calibration registers.