CS4271 Datasheet, PDF (32/53 Pages) Cirrus Logic – 24-Bit, 192 kHz Stereo Audio CODEC

CS4271
5.4 Analog Connections
5.4.1 Input Connections
The analog modulator samples the input at 6.144 MHz (MCLK=12.288 MHz). The digital filter will reject signals with-
in the stopband of the filter. However, there is no rejection for input signals which are (n × 6.144 MHz) the digital
passband frequency, where n=0,1,2,... Refer to Figure 12 for a recommended analog input buffer that will attenuate
any noise energy at 6.144 MHz, in addition to providing the optimum source impedance for the modulators. The use
of capacitors which have a large voltage coefficient (such as general purpose ceramics) must be avoided since
these can degrade signal linearity. Figure 13 shows the full-scale analog input levels.
AINL
10 µF
10 kΩ
470 pF
634 Ω
C0G
-
91 Ω
+
2700 pF
C0G
CS4271
AINA
VQ2
-
+
1 µF
0.1 µF
VQ1
AINR
10 kΩ
10 µF
+
-
91 Ω
470 pF
C0G
634 Ω
2700 pF
C0G
VQ3
AINB
Figure 12. CS4271 Recommended Analog Input Buffer
3.9 V
2.5 V
1.1 V
3.9 V
2.5 V
1.1 V
CS4271
AINA
AINB
Full-Scale Input Level = 2.8 Vpp
Figure 13. Full-Scale Analog Input
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