CS4811 データシートの表示（PDF） - Cirrus Logic
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CS4811 Datasheet PDF : 24 Pages
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CS4811
3.3 Analog Outputs
3.3.1 Line Level Outputs
The CS4811 contains on-chip differential buffer
amplifiers that produce line level outputs AOUT+
and AOUT-, which are capable of driving 10 kΩ
loads. These amplifiers are internally biased to the
CMOUT voltage of 2.3 V.
The recommended off-chip analog filter is a 2nd
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 fil-
tering is desired. These filters can be easily inte-
grated into a differential-to-single-ended converter
circuit as shown in the 2-pole and 3-pole Butter-
worth filters of Figure 7. Figure 8 shows the rec-
14.0 k Ω
AOU T-
14.0 k Ω
AOU T+
14.0 k Ω
3.24 k Ω
1000 pF
3.24 k Ω
220 pF
+5 V
_
+
GND
BUFFERED
CMOUT
1000 pF
14.0 k Ω 220 pF
2-Pole Butterworth Filter
Example
Op-Amps
are
MC33078
Line
MUTE
Out
ommended mute circuit referenced in Figure 7.
Activating the mute circuit is recommended on
power-up and power-down to avoid the output of
undesirable audio signals.
3.4 Clock Generation
The master clock to operate the CS4811 may be gen-
erated by using the on-chip oscillator with an exter-
nal crystal or may be input from an external clock
source.
3.4.1 Clock Source
The CS4811 requires a 256 Fs master clock to run
the internal logic. The two possible clock sources
are the on-chip crystal oscillator or an external clock
input to the XTI pin.
The master clock may be generated directly from
the on-chip crystal oscillator circuit. When using
the on-chip crystal oscillator, external loading ca-
pacitors are required. (see Figure 3) High frequen-
cy crystals (>8 MHz) should be parallel resonant,
fundamental mode and designed for 20 pF loading.
(equivalent to 40 pF to ground on each leg)
The master clock may also be generated directly
from an external CMOS clock input to the XTI pin.
14.0kΩ
220 pF
2.8kΩ 11.0kΩ
AOU T-
2.8kΩ
2200 pF
2200 pF
2.8kΩ 11.0kΩ
AOU T+
2.8kΩ
+5 V
_
+
GND
BUFFERED
CMOUT
2200 pF
2200 pF
220 pF
14.0kΩ
3-Pole Butterworth Filter
MUTE
Line
Out
From
CS4811
PIO
1 kΩ 10 µF
+
Line Out
VA
MMBT3906
10 kΩ
3.3 kΩ
MMBT3904
10 kΩ
10 µF
10 kΩ
MMBT3906
GND
Figure 7. Butterworth Output Filters
Figure 8. Output Mute Circuit
DS486PP2
13
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