Datasheet

AD7321 Data Sheet
Rev. B | Page 20 of 36
±16
.5
V
V
DD
/V
S
S
±
12V
V
DD
/V
S
S
5
–6
V
COM
RANGE (V)
4
3
2
1
0
–1
–
2
–
3
–
4
–5
V
CC
= 3
V
V
RE
F
=
3V
±
2.
5V
RANG
E
±10V
RANG
E
±5
V
RANG
E
±
2.
5
V
RANGE
±
5
V RAN
GE
±10
V
RANG
E
05399-045
Figure 35. Common-Mode Range for V
CC
= 3 V and REFIN/OUT = 3 V
±16.
5V V
DD
/V
SS
±
12V V
DD
/V
SS
V
COM
RANGE (V)
V
CC
= 5
V
V
REF
= 3
V
8
–4
6
4
2
0
–2
±2.
5V
RANGE
±10
V
RAN
GE
±
5V
RANG
E
±
2.5
V
RAN
GE
±
5
V RAN
GE
±10
V
RAN
GE
05399-046
Figure 36. Common-Mode Range for V
CC
= 5 V and REFIN/OUT = 3 V
6
–8
4
2
0
–2
–4
–6
±16.5V V
DD
/V
SS
±12V V
DD
/V
SS
V
COM
RANGE (V)
V
CC
= 3V
V
R
EF
= 2.5V
±
2.5V
RANGE
±10V
RANGE
±5V
RANGE
±2
.5V
RANG
E
±5V RANGE
±10
V
RANGE
05399-047
Figure 37. Common-Mode Range for V
CC
= 3 V and REFIN/OUT = 2.5 V
8
–8
6
4
2
0
–2
–4
–6
±16.5V V
DD
/V
SS
±12
V V
D
D
/
V
S
S
V
COM
RANGE (V)
V
C
C
= 5V
V
REF
= 2.5V
±
2.
5
V
RAN
G
E
±
10V
RANG
E
±5
V
RANG
E
±2.
5V
RANG
E
±
5
V RAN
GE
±
10V
RANG
E
05399-048
Figure 38. Common-Mode Range for V
CC
= 5 V and REFIN/OUT = 2.5 V
Pseudo Differential Inputs
The AD7321 can have one pseudo differential pair. The V
IN
+
inputs are coupled to the signal source and must have an amplitude
within the selected range for that channel as programmed in the
range register. A dc input is applied to the V
IN
− pin. The voltage
applied to this input provides an offset for the V
IN
+ input from
ground or a pseudo ground. Pseudo differential inputs separate
the analog input signal ground from the ADC ground, allowing
cancellation of dc common-mode voltages.
When a conversion takes place, the pseudo ground corresponds
to Code −4096, and the maximum amplitude corresponds to
Code +4095.
AD732
1
1
V
IN
+
V+
V–
V
DD
V
SS
V
CC
5V
1
ADDIT
IONA
L PINS OMITTED
FOR C
LARI
TY.
V
I
N
–
05399-028
Figure 39. Pseudo Differential Inputs
Figure 40 and Figure 41 show the typical voltage range on the
V
IN
− pin for the different analog input ranges when configured
in the pseudo differential mode.
For example, when the AD7321 is configured to operate in
pseudo differential mode and the ±5 V range is selected with
±16.5 V V
DD
/V
SS
supplies and 5 V V
CC
, the voltage on the V
IN
−
pin can vary from −6.5 V to +6.5 V.
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