AD7322 Analog Devices, AD7322 Datasheet - Page 18

• Manufacturer Part Number: AD7322
• Description: Software Selectable True Bipolar Input, 2-Channel, 12-Bit Plus Sign ADC
• Manufacturer: Analog Devices

Specifications of AD7322

• Resolution (bits): 13bit
• # Chan: 2
• Sample Rate: 1MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Bip,Diff-Uni,SE-Uni
• Ain Range: Bip (Vref),Bip (Vref) x 2,Bip (Vref) x 4,Bip 10V,Bip 2.5V,Bip 5.0V,Uni (Vref) x 4,Uni 10V
• Adc Architecture: SAR
• Pkg Type: SOP

AD7322
TYPICAL CONNECTION DIAGRAM
Figure 32 shows a typical connection diagram for the AD7322.
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
AD7322 can be configured to operate in single-ended, true
differential, or pseudo differential mode. The AD7322 can operate
with either an internal or external reference. In Figure 32, the
AD7322 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
5 V supply voltage. V
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 Table 6). The V
pin is connected to the supply voltage of the microprocessor.
The voltage applied to the V
the serial interface. V
+15V
–15V
ANALOG INPUT
Single-Ended Inputs
The AD7322 has a total of two 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 33 shows the configuration of the AD7322 in single-
ended mode.
ANALOG INPUTS
±10V, ±5V, ±2.5V
0V TO +10V
CC
680nF
pin can be connected to either a 3 V supply voltage or a
0.1µF
0.1µF
+
+
Figure 32. Typical Connection Diagram
10µF
10µF
V
V
REFIN/OUT
IN
IN
0
1
V
DD
V
DD
DRIVE
1
AD7322
SS
1
MINIMUM V
DEPEND ON THE HIGHEST ANALOG INPUT
RANGE SELECTED.
1
and V
can be set to 3 V or 5 V.
DRIVE
AGND
V
CC
V
DGND
SS
DOUT
SCLK
DRIVE
DD
DIN
are the dual supplies for the
10µF
CS
AND V
input controls the voltage of
10µF
+
SS
0.1µF
SUPPLY VOLTAGES
+
0.1µF
INTERFACE
SERIAL
+3V SUPPLY
V
CC
µC/µP
+2.7V TO +5.25V
DRIVE
Rev. A | Page 18 of 36
True Differential Mode
The AD7322 can have a total of one true differential analog
input pair. 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 34 defines the configuration of
the true differential analog inputs of the AD7322.
The amplitude of the differential signal is the difference
between the signals applied to the V
each differential pair (V
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
differential signal is −20 V to +20 V p-p (2 × 4 × V
regardless of the common mode.
The common mode is the average of the two signals
and is therefore the voltage on which the two input signals
are centered.
This voltage is set up externally, and its range varies with
reference voltage. As the reference voltage increases, the
common-mode range decreases. When driving the differential
inputs with an amplifier, the actual common-mode range is
determined by the amplifier’s output swing. If the differential
inputs are not driven from an amplifier, the common-mode
range is determined by the supply voltage on the V
and the V
(V
AGND
Figure 33. Single-Ended Mode Typical Connection Diagram
IN
+ + V
SS
NOTES
1. V
1
ADDITIONAL PINS OMITTED FOR CLARITY.
supply pin.
IN
IN
+ REFERS TO V
−)/2
Figure 34. True Differential Inputs
1
ADDITIONAL PINS OMITTED FOR CLARITY.
IN
+ − V
V+
V–
IN
REF
0 AND V
V
V
IN
mode, the amplitude of the
IN
IN
−). V
+
–
IN
AD7322
– REFERS TO V
IN
+ and V
IN
V
+ and V
IN
0
AD7322
1
IN
V
− inputs in
V
IN
IN
DD
SS
1
1.
− should
REF
DD
V
5V
CC
),
supply pin