Datasheet

AD7323 Data Sheet
Rev. B | Page 20 of 36
When a conversion takes place, the common mode is rejected,
resulting in a noise-free signal of amplitude −2 × (4 × V
REF
)
to +2 × (4 × V
REF
) corresponding to Digital Code −4096 to
Digital Code +4095.
±16.
5V V
DD
/
V
SS
±12V V
DD
/
V
SS
5
–6
V
COM
RANGE (V)
4
3
2
1
0
–
1
–2
–
3
–4
–
5
V
C
C
= 3
V
V
R
EF
= 3V
±2.5V
RANG
E
±10V
RANGE
±5V RANGE
±2
.
5V
RAN
G
E
±
5
V RAN
GE
±
10
V
RANG
E
05400-045
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
= 5V
V
REF
= 3V
8
–4
6
4
2
0
–2
±2.5V
RANGE
±10V
RANGE
±5V RANGE
±2.5V
RANGE
±5V RANGE
±10V
RANGE
05400-046
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
REF
= 2.5V
±2.5V
RANGE
±10V
RANGE
±5V RANGE
±2.5V
RANGE
±5V RANGE
±10V
RANGE
05400-047
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
±12V V
DD
/V
SS
V
COM
RANGE (V)
V
CC
= 5V
V
REF
= 2.5V
±2.5V
RANGE
±10V
RANGE
±5V RANGE
±2.5V
RANGE
±5V RANGE
±10V
RANGE
05400-048
Figure 38. Common-Mode Range for V
CC
= 5 V and REFIN/OUT = 2.5 V
Pseudo Differential Inputs
The AD7323 can have two pseudo differential pairs or three
pseudo differential inputs referenced to a common V
IN
− input.
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
− input. 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.
AD7323
1
V
IN
+
V+
V–
V
DD
V
SS
V
CC
5V
V
IN
–
05400-028
1
ADDITIONAL PINS OMITTED FOR CLARITY.
NOTES
1. V
IN
+ CAN BE V
IN
0, V
IN
1, OR V
IN
2, AND V
IN
– CAN BE V
IN
1
OR V
IN
3.
Figure 39. Pseudo Differential Inputs
Figure 40 and Figure 41 show the typical voltage range on the
V
IN
− input for the different analog input ranges when
configured in the pseudo differential mode.
For example, when the AD7323 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
−
input can vary from −6.5 V to +6.5 V.