CS4812
of driving 10 kΩ loads to full scale. These amplifi-
ers internally biased to the CMOUT voltage of 2.3
V.
150
Ω
CS4812
AIN
22 µF
2.2 nF
The recommended off-chip analog filter is a second
order Butterworth with a 3 dB corner at Fs. A third
order Butterworth filter with a -3 dB corner at 0.75
Fs can be used if greater out of band noise filtering
is desired. These filters can be easily integrated into
a differential-to-single-ended converter circuit as
shown in the 2-pole and 3-pole Butterworth filters
of Figure 12. The hardware mute circuit referenced
in Figure 12 is shown in Figure 13. Hardware mut-
ing is recommended on power-up and power-
down.
AIN
+
100 µF
0.1 µF
Figure 11. Single Ended Input
signal swing. DC control input voltages may range
from ground to Vcc.
ADC output data is in twos-complement binary
format. For inputs above full scale, the ADC digital
output saturates. The OVL output pin asserts when
the analog input is out-of-range.
220 pF
Ω
14.0 k
+5 V
GND
Ω
Ω
Ω
3.24 k
14.0 k
14.0 k
_
+
A
OU
T-
Output
Mute Ckt
Line
Out
3.2.2 Digital High Pass Filter
1
00 pF
0
In DC coupled systems, a small DC offset may ex-
ist between the input circuitry and the A/D convert-
ers. The CS4812 includes a defeatable high pass
filter after the decimator to remove these DC com-
ponents. The high pass filter response is given in
“High Pass Filter Characteristics” on page 4 and
scales linearly with sample rate. In applications
where DC level measurement is required, as would
occur when one of the ADC inputs is used for mea-
surement of DC control voltages, the high pass fil-
ter may be disabled via a control port register.
Note: The high pass filter defeat operates on both
ADC inputs simultaneously therefore external DC
blocking must be provided in the design of the an-
alog audio input circuit.
Ω
3.24 k
A
OUT+
Ω
14.0 k
220 pF
1000pF
BUFFERED
CMOUT
2-Pole Butterworth Filter
220
pF
Ω
Ω
14.0k
+5 V
Ω
2.8k
Ω
11.0k
2.8k
_
A
OU T-
Output
Mute Ckt
Line
Out
+
2200 pF
2200 pF
GND
Ω
2.8k
Ω
Ω
2.8k 11.0k
A
OUT+
2200 pF
220 pF
2200
pF
Ω
14.0k
BUFFERED
CMOUT
3.3
Analog Outputs
3-Pole Butterworth Filter
3.3.1 Line Level Outputs
The CS4812 contains on-chip differential buffer
amplifiers that produce line level outputs capable
Figure 12. Butterworth Output Filters
18
DS291PP3
CIRRUS [ CIRRUS LOGIC ]
