Datasheet

204
ATmega32A [DATASHEET]
Atmel-8155D-AVR-ATmega32A-Datasheet_02/2014
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 22-3 on page
222 and Table 22-4 on page 223). 0x000 represents analog ground, and 0x3FF represents the selected reference
voltage minus one LSB.
If differential channels are used, the result is
where V
POS
is the voltage on the positive input pin, V
NEG
the voltage on the negative input pin, GAIN the selected
gain factor, and V
REF
the selected voltage reference. The result is presented 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 results, it is suf-
ficient to read the MSB of the result (ADC9 in ADCH). If this bit is one, the result is negative, and if this bit is zero,
the result is positive. Figure 22-14 shows the decoding of the differential input range.
Table 22-2 shows the resulting output codes if the differential input channel pair (ADCn - ADCm) is selected with a
gain of GAIN and a reference voltage of V
REF
.
Figure 23-14. Differential Measurement Range
ADC
V
IN
1024
V
REF
--------------------------=
ADC
V
POS
V
NEG
–GAIN 512
V
REF
------------------------------------------------------------------------=
0
Output Code
0x1FF
0x000
V
REF
/GAIN
Differential Input
Voltage (Volts)
0x3FF
0x200
- V
REF
/GAIN