Datasheet

255
8272E–AVR–04/2013
ATmega164A/PA/324A/PA/644A/PA/1284/P
23.7.4 ADC Accuracy Definitions
An n-bit single-ended ADC converts a voltage linearly between GND and V
REF
in 2
n
steps
(LSBs). The lowest code is read as 0, and the highest code is read as 2
n
-1.
Several parameters describe the deviation from the ideal behavior:
• Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal transition (at
0.5LSB). Ideal value: 0LSB
Figure 23-10. Offset error.
• Gain Error: After adjusting for offset, the Gain Error is found as the deviation of the last
transition (0x3FE to 0x3FF) compared to the ideal transition (at 1.5LSB below maximum). Ideal
value: 0LSB
Figure 23-11. Gain error.
• Integral Non-linearity (INL): After adjusting for offset and gain error, the INL is the maximum
deviation of an actual transition compared to an ideal transition for any code. Ideal value: 0
LSB
Output Code
V
REF
Input Voltage
Ideal ADC
Actual ADC
Offset
Error
Output Code
V
REF
Input Voltage
Ideal ADC
Actual ADC
Gain
Error