CS4812 Cirrus Logic, CS4812 Datasheet - Page 18

• Manufacturer Part Number: CS4812
• Description: Fixed Function Multi-Effects Audio Processor
• Manufacturer: Cirrus Logic

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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.
3.2.2
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.
3.3
3.3.1
The CS4812 contains on-chip differential buffer
amplifiers that produce line level outputs capable
18
Analog Outputs
Digital High Pass Filter
Line Level Outputs
+
22 µF
100 µF
Figure 11. Single Ended Input
150
Ω
0.1 µF
2.2 nF
AIN
AIN
CS4812
of driving 10 k
ers internally biased to the CMOUT voltage of 2.3
V.
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.
BUFFERED
CMOUT
BUFFERED
CMOUT
A
A
OU T+
OU T-
Figure 12. Butterworth Output Filters
A
A
2200 pF
2200 pF
OU T-
OUT+
2.8k Ω
2.8kΩ
14.0 k Ω
14.0 k Ω
1000 pF
Ω
2200 pF
11.0k Ω
3-Pole Butterworth Filter
11.0k Ω
2-Pole Butterworth Filter
loads to full scale. These amplifi-
3.24 k Ω
1000 pF
14.0 k Ω
14.0k Ω
2200 pF
3.24 k Ω
14.0 k Ω
2.8k Ω
14.0k Ω
2.8k Ω
220 pF
220 pF
220 pF
_
+
220 pF
_
+
+5 V
GND
+5 V
GND
Mute Ckt
CS4812
Mute Ckt
Output
Output
DS291PP3
Line
Out
Line
Out