Datasheet

AD7329 Data Sheet
Rev. B | Page 22 of 40
Pseudo Differential Inputs
The AD7329 can have four pseudo differential pairs or seven
pseudo differential inputs referenced to a common V
IN
− pin.
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 pseudo ground. Pseudo differential
inputs separate the analog input signal ground from the ADC
ground, allowing cancellation of dc common-mode voltages.
Figure 42 shows the configuration of the AD7329 in pseudo
differential mode.
When a conversion takes place, the pseudo ground corresponds
to Code −4096 and the maximum amplitude corresponds to
Code +4095.
AD7329
1
V
IN
+
V+
V–
V
DD
V
SS
V
CC
5V
1
ADDITIONA
L PINS OMITTED FOR CLARITY.
V
IN
–
05402-039
Figure 42. Pseudo Differential Inputs
Figure 43 and Figure 44 show the typical voltage range on the
V
IN
− pin for various analog input ranges when configured in
the pseudo differential mode.
For example, when the AD7329 is configured to operate in
pseudo differential mode and the ±5 V range is selected with
16.5 V V
DD
, −16.5 V V
SS
, and 5 V V
CC
, the voltage on the V
IN
−
pin can vary from −6.5 V to +6.5 V.
05402-040
8
–8
6
4
2
0
–2
–4
–6
±2.5V
RANGE
±10V
RANGE
±10V
RANGE
±5V RANGE
±2.5V
RANGE
±5V RANGE
0V
TO +10V
RANGE
0V TO +10V
RANGE
±16.5V V
DD
/V
SS
±12V V
DD
/V
SS
V
CC
= 5V
V
REF
= 2.5V
Figure 43. Pseudo Differential Input Range with V
CC
= 5 V
05402-041
±2.5V
RANGE
±10V
RANGE
±10V
RANGE
±5V RANGE
±2.5V
RANGE
±5V RANGE
0V TO +10V
RANGE
0V TO +10V
RANGE
±16.5V V
DD
/V
SS
±12V V
DD
/V
SS
4
–8
2
0
–2
–4
–6
V
CC
= 3V
V
REF
= 2.5V
Figure 44. Pseudo Differential Input Range with V
CC
= 3 V