atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 238

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

18.7
238
ADC Conversion Result
ATmega32/64/M1/C1
Figure 18-13. Differential Non-linearity (DNL)
•
•
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
Table 18-4 on page 242
0x3FF represents the selected reference voltage.
If differential channels are used, the result is:
where V
GAIN the selected gain factor and V
in two’s complement form, from 0x200 (-512d) through 0x1FF (+511d). Note that if the user
wants to perform a quick polarity check of the result, it is sufficient to read the MSB of the result
(ADC9 in ADCH). If the bit is one, the result is negative, and if this bit is zero, the result is posi-
tive.
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.
Figure 18-14
IN
POS
is the voltage on the selected input pin and V
is the voltage on the positive input pin, V
Output Code
shows the decoding of the differential input range.
0x000
0x3FF
and
0
Table 18-5 on page
1 LSB
ADC
REF
ADC
=
the selected voltage reference. The result is presented
(
----------------------------------------------------------------------- -
V
POS
=
V
--------------------------
–
IN
V
243). 0x000 represents analog ground, and
V
⋅
REF
NEG
1023
NEG
V
REF
REF
) GAIN 512
⋅
the voltage on the negative input pin,
the selected voltage reference (see
⋅
V
REF
Input Voltage
7647A–AVR–02/08