ADS7822

12-Bit A/D

DCLOCK

D

OUT

CS/SHDN

1/2

OPA2348

+5V

V

IN

V+

2

+In

3

–In

V

REF

8

4

GND

Serial

Interface

1

0.1µF

0.1µF

7

6

5

NOTE: A/D Input = 0 to V

REF

V

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

1000pF

Electret

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

typical quiescent current.

Figure 8. Speech Bandpass Filtered Data Acquisition System

10

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