CS4207 Datasheet, PDF (139/144 Pages) Cirrus Logic – Low-power, 4-in / 6-out HD Audio CODEC with Headphone Amp

CS4207
8. ANALOG OUTPUT AND FILTERING
The Cirrus Application Note titled Design Notes for a 2-Pole Filter with Differential Input, available as AN48 at
www.cirrus.com, discusses the second-order Butterworth filter and differential-to-single-ended converter that was
implemented on the CS4207 evaluation board. Figure 9 illustrates this implementation. If only single-ended outputs
from the CS4207 are required, the passive output filter shown in Figure 10 can be used.
CS4207
LINEOUTx -
3300 pF _{2.26 kΩ}
22 μF
C0G
4.53 kΩ
1.5 kΩ
1000 pF
C0G
-
220 Ω
LINEOUTx +
AGND
22μF 2.05 kΩ
6800 pF
C0G
698 Ω
1.05 kΩ
+
2200 pF
C0G
Figure 9. Differential to Single-Ended Output Filter
Analog
Output
220 pF
CS4207
LINEOUTx +
4.7 µF
+
562 Ω
47.5 kΩ
2700 pF
Analog
Output
AGND
Figure 10. Passive Single-Ended Output Filter
9. PCB LAYOUT CONSIDERATIONS
9.1 Power Supply, Grounding
As with any high-resolution converter, the CS4207 requires careful attention to power supply and grounding
arrangements if its potential performance is to be realized. Figure 1 on page 11 and Figure 2 on page 12
show the recommended power arrangements, with VA connected to a clean supply. VD, which powers the
digital circuitry, may be run from the system logic supply.
To achieve full analog performance, it is strongly recommended that the following rules be followed:
• place the cap between VBIAS and VA_REF as close to the codec as possible to minimize trace imped-
ance
• keep the traces for VA and VA_REF separate as much as possible and only connect them at the supply
Extensive use of power and ground planes, ground plane fill in unused areas and surface mount decoupling
capacitors are recommended. Decoupling capacitors should be as close to the pins of the CS4207 as pos-
sible. The low value ceramic capacitor should be closest to the pin and should be mounted on the same
side of the board as the CS4207 to minimize inductance effects. All signals, especially clocks, should be
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