CS4294-JQ CIRRUS [Cirrus Logic], CS4294-JQ Datasheet - Page 31

• Manufacturer Part Number: CS4294-JQ
• Description: SoundFusion Audio/Docking Codec 97 (AMC 97)
• Manufacturer: CIRRUS [Cirrus Logic]

7.3 Line Level Outputs
The analog output section provides a stereo line-
level output and an alternate stereo line-level out-
put.
ALT_LINE_OUT_L, and ALT_LINE_OUT_R
outputs should be capacitively coupled to external
circuitry.
Each of the 4 analog outputs, if used in the design,
require 680 pF or larger NPO dielectric capacitors
between the corresponding pin and AGND. Each
analog output is DC biased up to the Vrefout volt-
age signal reference which is nominally 2.2 V. This
requires that the output either be AC coupled to ex-
ternal circuitry (AC load must be greater than 10
k ) or DC coupled to a buffer op-amp biased at the
Vrefout voltage (see Figure 13 for the recommend-
ed headphone op-amp circuit).
7.4 Miscellaneous Analog Signals
The AFILT1 and AFILT2 pins must have a
1000 pF NPO capacitor (must not be smaller than
DS326PP4
LINE_OUT_L,
4
3
5
2
1
AGND
CGND
Figure 12. PC ‘99 Microphone Pre-amplifier
220 pF
LINE_OUT_R,
2.7 k
220 pF
X7R
68 k
0.068 µF
AGND
+
AGND
1
2
100 k
390 pF) to analog ground. These capacitors, along
with an internal resistor, provide a single-pole low-
pass filter at the inputs to the ADCs. By placing
these filters at the input to the ADCs, low-pass fil-
ters at each analog input pin are not necessary.
The REFFLT pin lowers the noise of the internal
voltage reference. A 1 F (must not be greater than
1 F) and 0.1 F capacitor to analog ground should
be connected with a short, wide trace to this pin. No
other connection should be made, as any coupling
onto this pin will degrade the analog performance
of the Codec. Likewise, digital signals should be
kept away from REFFLT for similar reasons.
The Vrefout pin is typically 2.2 V and provides a
common mode signal for single-supply external
circuits. Vrefout only supports light DC loads and
should be buffered if AC loading is needed. For
typical use, a 0.1 F in parallel with a 1 F capaci-
tor should be connected to Vrefout.
1
10 µF
AGND
+5 VA
4
8
+
-
6.8 k
3
2
47 k
U1A
MC33078D
5
6
+
AGND
AGND
+
+5 VA
-
1
2
220 pF
8
4
47 k
10 µF
7
U1B
MC33078D
AGND
+5 VA
47 k
47 k
X7R
1 µF
CS4294
MIC1
31