Datasheet

132
ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
Figure 17-12. Differential Non-linearity (DNL)
• Quantization Error: Due to the quantization of the input voltage into a finite number of codes, a range of input
voltages (1 LSB wide) will code to the same value. Always ± 0.5 LSB.
• Absolute Accuracy: The maximum deviation of an actual (unadjusted) transition compared to an ideal transition
for any code. This is the compound effect of offset, gain error, differential error, non-linearity, and quantization
error. Ideal value: ± 0.5 LSB.
17.11 ADC Conversion Result
After the conversion is complete (ADIF is high), the conversion result can be found in the ADC Result Registers
(ADCL, ADCH). The form of the conversion result depends on the type of the conversio as there are three types of
conversions: single ended conversion, unipolar differential conversion and bipolar differential conversion.
17.11.1 Single Ended Conversion
For single ended conversion, the result is
where V
IN
is the voltage on the selected input pin and V
REF
the selected voltage reference (see Table 17-3 on page
134 and Table 17-4 on page 135). 0x000 represents analog ground, and 0x3FF represents the selected voltage
reference minus one LSB. The result is presented in one-sided form, from 0x3FF to 0x000.
17.11.2 Unipolar Differential Conversion
If differential channels and an unipolar input mode are used, the result is
Output Code
0x3FF
0x000
0
V
REF
Input Voltage
DNL
1 LSB
ADC
V
IN
1024
V
REF
--------------------------=