Datasheet
ADS7822
12-Bit A/D
DCLOCK
D
OUT
CS/SHDN
1/2
OPA2348
+5V
V
IN
V+
2
+In
3
–In
V
REF
8
4GND
Serial
Interface
1
0.1µF 0.1µF
7
6
5
NOTE: A/D Input = 0 to V
REF
V
IN
= 0 V to 5 V for
0-V to 5-V output.
RC network filters high-frequency noise.
500W
3300pF
C
3
33pF
V
+
GND
3
1
8
4
5
6
7
–IN
+IN
2
C
2
DCLOCK
Serial
Interface
1000pF
R
1
1.5kW
R
4
20kW
R
5
20kW
R
6
100kΩ
R
8
150kW
R
9
510kW
R
7
51kW
D
OUT
V
REF
V+ = +2.7V to 5V
CS/SHDN
C
1
1000pF
Electret
Microphone
(1)
G = 100
Passband 300Hz to 3kHz
R
3
1MW
R
2
1MW
(1) Electret microphone powered by R .
1
ADS7822
12-Bit A/D
1/2
OPA2348
1/2
OPA2348
OPA2348-Q1
OPA4348-Q1
SBOS465A –JANUARY 2009–REVISED MARCH 2010
www.ti.com
Driving Analog-to-Digital Converters (ADCs)
The OPA2348 op amps are optimized for driving medium-speed sampling ADCs. The OPA2348 op amps buffer
the ADC input capacitance and resulting charge injection while providing signal gain.
Figure 7 shows the OPA2348 in a basic noninverting configuration driving the ADS7822. The ADS7822 is a
12-bit, micropower sampling converter in the MSOP-8 package. When used with the low-power miniature
packages of the OPA348, the combination is ideal for space-limited, low-power applications. In this configuration,
an RC network at the ADC input can be used to provide for anti-aliasing filter and charge injection current.
Figure 7. Noninverting Configuration Driving ADS7822
The OPA2348 can also be used in noninverting configuration driving ADS7822 in limited low-power applications.
In this configuration, an RC network at the ADC input can be used to provide for antialiasing filter and charge
injection current. See Figure 7 for the OPA2348 driving an ADS7822 in a speech bandpass filtered data
acquisition system. This small low-cost solution provides the necessary amplification and signal conditioning to
interface directly with an electret microphone. This circuit operates with V
S
= 2.7 V to 5 V with less than 250-µA
typical quiescent current.
Figure 8. Speech Bandpass Filtered Data Acquisition System
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Product Folder Link(s): OPA2348-Q1 OPA4348-Q1