Cirrus Logic AN234 - Manual (Page 5)

AN234
5
Figure 3. Single-Ended to Differential Input Buffer
8.2 Fully Differential Input Buffer
Figure 4 shows a fully differential analog input buffer. This buffer provides the proper biasing, isolation
from the switched capacitor currents, low output impedance, and anti-alias filtering. This input buffer is
unity gain, so a 5.6 Vpp differential input will provide a full-scale 5.6 Vpp differential input into the CS5381.
Figure 4. Fully Differential Input Buffer
VA
+
+
-
-
1 µ F
100 k Ω
100 k Ω
3.3 k Ω
3.3 k Ω
0.01 µ F 100 µ F
470 pF
470 pF
C0G
C0G
634 Ω
634 Ω
634 Ω
91 Ω
91 Ω
2700 pF
C0G
0.01 µ F 1 µ F
AIN+
AIN-
VQ
CS5381
AIN+
AIN-
VA
+
+
-
-
1 µ F
100 k Ω
100 k Ω
3.3 k Ω
3.3 k Ω
0.01 µ F 100 µ F
470 pF
470 pF
C0G
C0G
634 Ω
634 Ω
634 Ω
91 Ω
91 Ω
2700 pF
C0G
AIN+
AIN-
VQ
-
+
-
+
470 pF
C0G
470 pF
C0G
CS5381
634 Ω
91 Ω
634 Ω
91 Ω
2700 pF
C0G
10 µ F
10 µ F
10 k Ω
10 k Ω
0.01 µ F
1 µ F 0.01 µ F
100 k Ω
100 k Ω
-
+
-
470 pF
C0G
470 pF
C0G
634 Ω
91 Ω
634 Ω
91 Ω
2700 pF
C0G
10 µ F
10 k Ω
10 k Ω
0.01 µ F
100 k Ω
AIN+
AIN-
100 k Ω
10 µ F
+
-