Appendix a: external filters, 1 adc input filter, Figure 24. recommended analog input buffer – Cirrus Logic CS42418 User Manual
Page 61: 2 dac output filter, Figure 25. recommended analog output buffer, 1 adc input filter 8.2 dac output filter, Put levels. see, Ainl ainr, Aout + aout
DS603F2
61
CS42418
8. APPENDIX A: EXTERNAL FILTERS
8.1
ADC Input Filter
The analog modulator samples the input at 6.144 MHz (internal MCLK=12.288 MHz). The digital filter will
reject signals within 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
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 that have a large voltage coefficient (such as
general-purpose ceramics) must be avoided since these can degrade signal linearity.
8.2
DAC Output Filter
The CS42418 is a linear phase design and does not include phase or amplitude compensation for an exter-
nal filter. Therefore, the DAC system phase and amplitude response will be dependent on the external an-
alog circuitry.
V A
+
+
-
-
100 F
100 k
10 k
3.32 k
2.8 k
0.1 F
100 F
470 pF
470 pF
C0G
C0G
634
634
634
91
91
2700 pF
C0G
AINL1+
AINL1-
AINR1+
AINR1-
VA
+
+
-
-
100 F
100 k
10 k
3.32 k
2.8 k
0.1 F
100 F
470 pF
470 pF
C0G
C0G
634
634
634
91
91
2700 pF
C0G
332
332
Figure 24. Recommended Analog Input Buffer
AINL
AINR
AOUT +
AOUT -
-
+
390 pF
C0G
1 k
22
F
6.19 k
1800 pF
C0G
887
2.94 k
5.49 k
1.65 k
1.87 k
22
F
1200 pF
C0G
5800 pF
C0G
47.5 k
Analog
Out
Figure 25. Recommended Analog Output Buffer