OPA832 datasheet(16/30 Pages) NSC

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OPA832

SBOS266E − JUNE 2003 − REVISED AUGUST 2008

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SINGLE-SUPPLY ADC INTERFACE

The circuit shown in Figure 6 uses the OPA832 as a dif-

ferential driver followed by an RC filter. In this circuit, the

single-ended to differential conversion is realized by a

1:1 transformer driving the noninverting inputs of the

two OPA832s. The common-mode level (CML) of the

ADS5203 is reduced to the appropriate input level of

0.885V by the network divider composed of R1 and the

CML output impedance, and connected to the trans-

former center tap, biasing the OPA832s. This input bias

voltage is then amplified to provide the correct com-

mon-mode voltage to the input of the ADC. Using only

25.1mW power (3.8mA

× 2 amplifiers × 3.3V), this con-

figuration (amplifier + ADC) provides greater than 59dB

SNR and 70dB SFDR to 2MHz, with all the components

running on a low +3.3V supply.

400

Ω

400

Ω

15pF

0.1

µF

CML

1/2

ADS5203

10−Bit

40MSPS

OPA832

+3.3V

400

Ω

400

Ω

1.91k

Ω

1:1

2.3k

Ω

Output

Impedance

Ω

Source

CM =0.885V

Figure 6. Low-Power, Single-Supply ADC Driver

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