OPA373_16 Datasheet, PDF (11/37 Pages) Texas Instruments – CMOS Operational Amplifier

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DRIVING ADCs
The OPA373 and OPA374 series op amps are optimized
for driving medium-speed sampling ADCs. The OPA373
and OPA374 op amps buffer the ADC input capacitance
and resulting charge injection, while providing signal gain.
The OPA373 is shown driving the ADS7816 in a basic
noninverting configuration, as shown in Figure 7. The
ADS7816 is a 12-bit, MicroPower sampling converter in
the MSOP-8 package. When used with the low-power,
miniature packages of the OPA373, 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 anti-aliasing filtering.
OPA373, OPA2373
OPA374
OPA2374, OPA4374
SBOS279E − SEPTEMBER 2003 − REVISED MAY 2008
Figure 8 shows the OPA373 driving the ADS7816 in a
speech band-pass 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 will operate with
V_S = 2.7V to 5V.
The OPA373 is shown in the inverting configuration
described in Figure 9. In this configuration, filtering may be
accomplished with the capacitor across the feedback
resistor.
ENABLE/SHUTDOWN
OPA373 and OPA374 series op amps typically require
585µA quiescent current. The enable/shutdown feature of
the OPA373 allows the op amp to be shut off in order to
reduce this current to less than 1µA.
+5V
0.1µF
0.1µF
V_IN
V_IN = 0V to 5V for
0V to 5V output.
OPA373
500Ω
3300pF
8 V+
1 V_REF
7
DCLOCK
+In
2
−In
ADS7816
6
12−Bit ADC
D_OUT
5
CS/SHDN
3
GND 4
Serial
Interface
f_SAMPLE = 100kHz
RC network filters high frequency noise.
NOTE: ADC Input = 0 to V_REF
Figure 7. The OPA373 in Noninverting Configuration Driving the ADS7816
R₁
1.5kΩ
C₁
1000pF
R₂
1MΩ
Electret
Microphone⁽¹⁾
R₃
1MΩ
V+ = +2.7V to +5V
R₄
20kΩ
1/2
OPA2373
R₆
100kΩ
R₇
51kΩ
R₉
510kΩ
R₈
150kΩ
C₃
33pF
C₂
1000pF
1/2
OPA2373
NOTE: (1) Electret microphone
powered by R₁.
R₅
20kΩ
G = 100
Passband 300Hz to 3kHz
V_REF 1
8 ^V+
7
+IN
ADS7816 ⁶
2
−IN
12−Bit ADC ₅
3
4 GND
DCLOCK
D _OUT
CS/SHDN
Serial
Interface
Figure 8. The OPA2373 as a Speech Bypass Filtered Data Acquisition System
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