CS5181

20

DS250PP1

APPENDIX A: CIRCUIT APPLICATIONS

Several amplifier circuits have been tested with the

CS5181. Performance at higher frequencies is gen-

erally limited by the operational amplifiers used to

drive the A/D converter.

Figure 12 illustrates a single operational amplifier

circuit which can accept a single-ended ground-ref-

erenced signal and condition it for the input of the

CS5181. The amplifier is AC-coupled to the signal

source. In this circuit the AIN- input to the CS5181

is held at a constant DC value and the AIN+ input

is driven (it is actually overdriven to achieve high

dynamic range, but this sacrifices performance

with regard to distortion). The common mode volt-

age for the CS5181 input should be designed to

stay between 1 V and VREF + 0.25 V when driven

at its AIN+ and AIN- inputs. The single amplifier

circuit in figure 12 has the disadvantages that the

common mode restriction limits the input signal

range and also causes errors due to variation in the

common mode voltage, as opposed to applying a

balanced differential signal.

Figures 13 and 14 illustrate the performance of the

the AIN+ input respectively.

0.15

C0G

10 k

Ω

+

-

+15

-15

20

Ω

+

AIN-

VREFOUT

CS5181

10 k

Ω

2200 pF

20

Ω

2200 pF

5 k

Ω

10 µF ++

10 µF

0.1 µF

1 k

Ω

AIN+

0.1 µF

0.1 µF

U1

Figure 12. Single amplifier driving only AIN+, with AIN- held at a steady dc value

Figure 13. Performance of amplifier of Figure 12 over-

Test Signal: 30.14 kHz @ -6 dB

S/N = 85.46 dB

S/D = 71.25 dB

S/N+D = 71.09 dB

8192 Samples

Figure 14. Performance of amplifier of Figure 12 with