Datasheet

AD7329 Data Sheet
Rev. B | Page 20 of 40
TYPICAL CONNECTION DIAGRAM
Figure 34 shows a typical connection diagram for the AD7329.
In this configuration, the AGND pin is connected to the analog
ground plane of the system, and the DGND pin is connected to
the digital ground plane of the system. The analog inputs on the
AD7329 can be configured to operate in single-ended, true
differential, or pseudo differential mode. The AD7329 can operate
with either an internal or external reference. In Figure 34, the
AD7329 is configured to operate with the internal 2.5 V reference.
A 680 nF decoupling capacitor is required when operating with
the internal reference.
The V
CC
pin can be connected to either a 3 V or a 5 V supply
voltage. The V
DD
and V
SS
are the dual supplies for the high
voltage analog input structures. The voltage on these pins must
be equal to or greater than the highest analog input range
selected on the analog input channels (see Tabl e 6 for more
information). The V
DRIVE
pin is connected to the supply voltage
of the microprocessor. The voltage applied to the V
DRIVE
input
controls the voltage of the serial interface.
AD7329
V
CC
V
DD
1
SERIAL
INTERFACE
FILTERING/BUFFERING
µC/µP
V
IN
0
V
IN
1
V
IN
2
V
IN
3
V
IN
4
V
IN
5
V
IN
6
V
IN
7
REF
IN
/REF
OUT
CS
DOUT
V
DRIVE
SCLK
DIN
DGND
10µF 0.1µF
+
MUX
OUT
+
ADC
IN
+
MUX
OUT
–
ADC
IN
–
10µF0.1µF
+
10µF0.1µF
+
ANALOG INPUTS:
±10V, ±5V, ±2.5V,
0V TO +10V
+15V
–15V
680nF
V
SS
1
V
CC
+2.7V TO +5.25V
1
MINIMUM V
DD
AND V
SS
SUPPLY VOLTAGES
DEPEND ON THE HIGHEST ANALOG INPUT
RANGE SELECTED.
AGND
05402-031
10µF 0.1µF
+
+3V SUPPLY
Figure 34. Typical Connection Diagram, Single-Ended Mode
AD7329
V
CC
V
DD
1
SERIAL
INTERFACE
FILTERING/BUFFERING
µC/µP
V
IN
0
V
IN
1
V
IN
2
V
IN
3
V
IN
4
V
IN
5
V
IN
6
V
IN
7
REF
IN
/REF
OUT
CS
DOUT
V
DRIVE
SCLK
DIN
DGND
10µF 0.1µF
+
MUX
OUT
–
MUX
OUT
+
ADC
IN
–
ADC
IN
+
10µF0.1µF
+
10µF0.1µF
ANALOG INPUTS:
±10V, ±5V, ±2.5V,
0V TO +10V
+15V
–15V
680nF
V
SS
1
V
CC
+2.7V TO +5.25V
1
MINIMUM V
DD
AND V
SS
SUPPLY VOLTAGES
DEPEND ON THE HIGHEST ANALOG INPUT
RANGE SELECTED.
AGND
05402-032
10µF 0.1µF
+
+3V SUPPLY
+
Figure 35. Typical Connection Diagram, Differential Mode
ANALOG INPUT
Single-Ended Inputs
The AD7329 has a total of eight analog inputs when operating
in single-ended mode. Each analog input can be independently
programmed to one of the four analog input ranges. In applications
where the signal source is high impedance, it is recommended
to buffer the signal before applying it to the ADC analog inputs.
Figure 36 shows the configuration of the AD7329 in single-
ended mode.
AD7329
1
V
IN
+
V+
V–
V
DD
V
SS
V
CC
5V
AGND
1
ADDITIONA
L PINS OMITTED FOR CLARITY
.
05402-033
Figure 36. Single-Ended Mode Typical Connection Diagram
True Differential Mode
The AD7329 can have four true differential analog input pairs.
Differential signals have some benefits over single-ended
signals, including better noise immunity based on the device’s
common-mode rejection and improvements in distortion
performance. Figure 37 defines the configuration of the true
differential analog inputs of the AD7329.
AD7329
1
V
IN
+
V
IN
–
1
ADDITIONAL PINS OMITTED FOR CLARITY.
05402-034
Figure 37. True Differential Inputs
The amplitude of the differential signal is the difference
between the signals applied to the V
IN
+ and V
IN
− pins in
each differential pair (V
IN
+ − V
IN
−). V
IN
+ and V
IN
− should
be simultaneously driven by two signals of equal amplitude,
dependent on the input range selected, that are 180° out of
phase. Assuming the ±4 × V
REF
mode, the amplitude of the
differential signal is −20 V to +20 V p-p (2 × 4 × V
REF
),
regardless of the common mode.
The common mode is the average of the two signals
(V
IN
+ + V
IN
−)/2
and is therefore the voltage on which the two input signals are
centered.