Datasheet

310
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
where V
IN
is the voltage on the selected input pin and V
REF
the selected voltage reference (see Table 24-3 on
page 313 and Table 24-4 on page 313). 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
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 positive. Figure 24-15 on page 311 shows the decoding of the differential input
range.
Table 82 shows the resulting output codes if the differential input channel pair (ADCn - ADCm) is selected with
a reference voltage of V
REF
.
ADC
V
IN
1023
V
REF
--------------------------
=
ADC
V
POS
V
NEG
–GAIN 512
V
REF
------------------------------------------------------------------------
=