190
ATmega8A [DATASHEET]
8159E–AVR–02/2013
Differential Non-linearity (DNL): The maximum deviation of the actual code width (the interval between two
adjacent transitions) from the ideal code width (1LSB). Ideal value: 0LSB.
Figure 23-11. 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 (1LSB wide) will code to the same value. Always ±0.5LSB.
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: ±0.5LSB.
23.7
ADC Conversion Result
After the conversion is complete (ADIF is high), the conversion result can be found in the ADC Result Registers
(ADCL, ADCH).
For single ended conversion, the result is
where V
IN is the voltage on the selected input pin and VREF the selected voltage reference (see Table 23-2 on page minus one LSB.
23.8
Register Description
23.8.1
ADMUX – ADC Multiplexer Selection Register – ADMUX
Bit 7:6 – REFS1:0: Reference Selection Bits
These bits select the voltage reference for the ADC, as shown in
Table 23-2. If these bits are changed during a
conversion, the change will not go in effect until this conversion is complete (ADIF in ADCSRA is set). The internal
voltage reference options may not be used if an external reference voltage is being applied to the AREF pin.
Output Code
0x3FF
0x000
0
VREF Input Voltage
DNL
1 LSB
ADC
VIN 1024
VREF
--------------------------
=
Bit
7654
3210
REFS1
REFS0
ADLAR
–
MUX3
MUX2
MUX1
MUX0
ADMUX
Read/Write
R/W
R
R/W
Initial Value
0000