ATA8741 ATMEL Corporation, ATA8741 Datasheet - Page 164

• Manufacturer Part Number: ATA8741
• Manufacturer: ATMEL Corporation

25.8
25.8.1
25.8.2
164
ADC Conversion Result
ATA8741
Single Ended Conversion
Unipolar Differential Conversion
Figure 25-12. Differential Non-linearity (DNL)
• Quantization Error: Due to the quantization of the input voltage into a finite number of codes, a
• Absolute Accuracy: The maximum deviation of an actual (unadjusted) transition compared to
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.
For single ended conversion, the result is
where V
Table 25-3 on page 166
0x3FF represents the selected reference voltage minus one LSB. The result is presented in
one-sided form, from 0x3FF to 0x000.
If differential channels and an unipolar input mode are used, the result is
where V
and V
range of input voltages (1 LSB wide) will code to the same value. Always ± 0.5 LSB.
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.
REF
IN
POS
the selected voltage reference. The voltage of the positive pin must always be larger
is the voltage on the selected input pin and V
is the voltage on the positive input pin, V
Output Code
0x000
0x3FF
and
ADC
0
Table 25-4 on page
=
1 LSB
---------------------------------------------------------- -
V
ADC
POS
–
=
V
V
V
---------------------------- -
NEG
REF
IN
V
REF
167). 0x000 represents analog ground, and
1024
1024
NEG
REF
the voltage on the negative input pin,
the selected voltage reference (see
GAIN
V
REF
Input Voltage
9140B–INDCO–07/09