CS5181 查看數據表（PDF） - Cirrus Logic
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CS5181 Datasheet PDF : 24 Pages
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CS5181
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
amplifier of Figure 12 operating with a 3.8 Vpp in-
put into the AIN+ input; and with 2.0 Vpp input into
the AIN+ input respectively.
Figure 13. Performance of amplifier of Figure 12 over-
driving AIN+ input to the CS5181 at 3.8 VPP
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
AIN+ driven at 2.0 VPP
+15
0.15
C0G
+
10 kΩ
10 kΩ
0.1 µF
-
U1
+
-15
20 Ω
2200 pF
0.1 µF
20 Ω
AIN+
CS5181
AIN-
5 kΩ
1 kΩ
10 µF +
2200 pF
+
VREFOUT
0.1 µF
10 µF
Figure 12. Single amplifier driving only AIN+, with AIN- held at a steady dc value
20
DS250PP1
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