18.6.4 ADC Accuracy Definitions
An n-bit single-ended ADC converts a voltage linearly between GND and VREF in 2n steps (LSBs). The lowest code is read
as 0, and the highest code is read as 2n-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 0.5 LSB). Ideal value:
0 LSB.
Figure 18-9. Offset Error
Output Code
Ideal ADC
Actual ADC
Offset
Error
V
Input Voltage
REF
●
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 1.5 LSB below maximum). Ideal value: 0 LSB
Figure 18-10. Gain Error
Output Code
Gain
Error
Ideal ADC
Actual ADC
V
Input Voltage
REF
ATmega16/32/64/M1/C1 [DATASHEET]
205
7647O–AVR–01/15
MICROCHIP [ MICROCHIP ]
