Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
1439
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
47.7.4 ADC Transfer Function
The first operation of the ADC is a sampling function relative to a common mode voltage. The common mode
voltage (VCM) is equal to V
voltage (VCM) is equal to V
ADVREF
/2 when the bits OFFx = 1, in Differential and in Single-ended mode. When the
bits OFFx
= 0, sampling is done versus V
ADVREF
/4 for gain = 2, and V
ADVREF
/8 for gain = 4, in Single-ended mode
only.
The code in AFEC_CDR is a 12-bit positive integer. The internal DAC is set for the code 2047.
47.7.4.1 Differential Mode
A differential input voltage
V
IN
=
V
INP
-
V
INN
can be applied between two selected differential pins, e.g. AD0 and
AD1.The ideal code Ci is calculated by using the following formula and rounding the result to the nearest positive
integer.
integer.
is a computation example for the above formula, where V
ADVREF
= 3V
:
47.7.4.2 Single-ended Mode
A single input voltage
V
IN
can be applied to selected pins, e.g. AD0 or AD1. The ideal code Ci is calculated by
using the following formula and rounding the result to the nearest positive integer.
The single-ended ideal code conversion formula for OFFx = 1 is:
is a computation example for the above formula, where V
ADVREF
= 3V:
The single-ended ideal code conversion formula for OFFx = 0 is:
Table 47-31.
Input Voltage Values in Differential Mode
Ci
Gain = 0.5
Gain = 1
Gain = 2
0
-3
-1.5
-0.75
2047
0
0
0
4095
3
1.5
0.75
C
i
4096
V
ADVREF
-----------------------
V
IN
×
Gain
2047
+
×
=
Table 47-32.
Input Voltage Values in Single-ended Mode, OFFx=1
Ci
Gain = 1
Gain = 2
Gain = 4
0
0
0.75
1.125
2047
1.5
1.5
1.5
4095
3
2.25
1.875
C
i
4096
V
ADVREF
-----------------------
V
IN
V
ADVREF
2
-----------------------
–
×
Gain
2047
+
×
=
C
i
V
IN
Gain
4096
V
ADVREF
-----------------------
1
–
×
×
=