AD7323BRUZ Analog Devices Inc, AD7323BRUZ Datasheet - Page 21

• Manufacturer Part Number: AD7323BRUZ
• Description: IC ADC 12BIT+ SAR 4CHAN 16TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7323BRUZ

• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Bits: 12
• Sampling Rate (per Second): 500k
• Number Of Converters: 1
• Power Dissipation (max): 17mW
• Voltage Supply Source: Dual ±
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP (0.173", 4.40mm Width)
• Resolution (bits): 13bit
• Sampling Rate: 500kSPS
• Input Channel Type: Pseudo Differential, Single Ended
• Supply Current: 900µA
• Digital Ic Case Style: TSSOP
• No. Of Pins: 16
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7323CBZ - BOARD EVALUATION FOR AD7323CBZ
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

DRIVER AMPLIFIER CHOICE
In applications where the harmonic distortion and signal-to-
noise ratio are critical specifications, the analog input of the
AD7323 should be driven from a low impedance source. Large
source impedances significantly affect the ac performance of the
ADC and can necessitate the use of an input buffer amplifier.
When no amplifier is used to drive the analog input, the source
impedance should be limited to low values. The maximum
source impedance depends on the amount of THD that can be
tolerated in the application. The THD increases as the source
impedance increases and performance degrades. Figure 21 and
Figure 22 show graphs of the THD vs. the analog input
frequency for various source impedances. Depending on the
input range and analog input configuration selected, the
AD7323 can handle source impedances of up to 5.5 kΩ before
the THD starts to degrade.
Due to the programmable nature of the analog inputs on the
AD7323, the choice of op amp used to drive the inputs is a
function of the particular application and depends on the input
configuration and the analog input voltage ranges selected.
–2
–4
–6
–8
–2
–4
–6
–8
8
6
4
2
0
4
2
0
V
V
V
V
CC
REF
CC
REF
Figure 40. Pseudo Input Range with V
Figure 41. Pseudo Input Range with V
= 5V
= 3V
RANGE
RANGE
= 2.5V
= 2.5V
±10V
±10V
±5V RANGE
±5V RANGE
±16.5V V
±16.5V V
RANGE
RANGE
±2.5V
±2.5V
DD
DD
0V TO +10V
0V TO +10V
/V
/V
RANGE
RANGE
SS
SS
RANGE
RANGE
±10V
±10V
±12V V
±12V V
±5V RANGE
±5V RANGE
DD
DD
CC
CC
/V
/V
SS
RANGE
SS
RANGE
= 5 V
= 3 V
±2.5V
±2.5V
0V TO +10V
0V TO +10V
RANGE
RANGE
Rev. A | Page 21 of 36
The driver amplifier must be able to settle for a full-scale step
to a 13-bit level, 0.0122%, in less than the specified acquisition
time of the AD7323. An op amp such as the
requirement when operating in single-ended mode. The AD8021
needs an external compensating NPO type of capacitor. The
AD8022 can also be used in high frequency applications where
a dual version is required. For lower frequency applications, op
amps such as the AD797, AD845, and
the AD7323 in single-ended mode configuration.
Differential operation requires that V
neously driven with two signals of equal amplitude that are 180°
out of phase. The common mode must be set up externally to the
AD7323. The common-mode range is determined by the REFIN/
OUT voltage, the V
used to drive the analog inputs. Differential mode with either an
ac input or a dc input provides the best THD performance over a
wide frequency range. Because not all applications have a signal
preconditioned for differential operation, there is often a need to
perform the single-ended-to-differential conversion.
This single-ended-to-differential conversion can be performed
using an op amp pair. Typical connection diagrams for an op
amp pair are shown in Figure 42 and Figure 43. In Figure 42,
the common-mode signal is applied to the noninverting input
of the second amplifier.
Figure 43. Single-Ended-to-Differential Configuration with the AD8021
Figure 42. Single-Ended-to-Differential Configuration with the AD845
V
COM
V
V
IN
IN
CC
100Ω
1.5kΩ
442Ω
supply voltage, and the particular amplifier
10kΩ
3kΩ
20kΩ
442Ω
442Ω
442Ω
442Ω
442Ω
1.5kΩ
1.5kΩ
1.5kΩ
AD8021
AD8021
AD845
AD845
IN
+ and V
AD8610
V+
V–
AD8021
V+
V–
IN
can be used with
− be simulta-
AD7323
meets this