ad1881a Analog Devices, Inc., ad1881a Datasheet - Page 24

• Manufacturer Part Number: ad1881a
• Description: Ac?97 Soundmax Codec
• Manufacturer: Analog Devices, Inc.

AD1881A
GROUNDING AND LAYOUT
To reduce noise and emissions, Analog Devices recommends a split ground plane as shown in Figure 16. The purpose of splitting the
ground plane is to create a low noise analog area that is somewhat isolated from the digital ground current noise generated by the
system’s logic. All the analog circuitry should be placed on the analog ground plane area.
For reference purposes, and to return power supply currents, the analog and digital ground planes must be connected at some point,
ideally a small bridge under or near the Codec should be provided. A 0 Ω resistor or a ferrite bead should also be considered since
these allow some flexibility in optimizing the layout to meet EMC requirements.
ANALOG POWER SUPPLY
To minimize audio noise, the Codec analog power supply (AVDD) should be well decoupled and regulated. In PC systems it is rec-
ommended that the analog supply be derived from the 12 V PC power supply using a localized linear voltage regulator. Preferably,
the analog power supply should be connected to the Codec’s analog section using a ferrite bead.
AD1881A
EAPD/CHAIN_IN
U1
LINE_OUT_L
MONO_OUT
LIN_OUT_R
0.33 F
0.33 F
C4
C7
49.9k
49.9k
ISOLATION
GROUND PLANE
R4
R6
TRENCH
DIGITAL
PIN 1
NC
LEFT IN
SHUTDOWN
SE/BTL
GND
RIGHT IN
NC
NC = NO CONNECT
SSM2250RU
49.9k
49.9k
AD1881A
R2
LEFT OUT/BLT
R7
U2
RIGHT OUT
BYPASS
BTL+
VDO
NC
NC
CONNECT SPLIT GROUND
PLANES AT OR NEAR CODEC.
GROUND PLANE
1 F
C1
ANALOG
5AV
DD
C8
0.1 F
100k
R1
100 F
100 F
C2
C5
R3
1k
R5
1k
600Z
600Z
FB
FB
F2
F1
C3
470pF
C6
470pF
LS1
4
STEREO
HP/SPEAKER
OUTPUT
INTERNAL
MONO
SPEAKER
STEREO
3.5mm JACK
J1