WM8725
Production Data
RECOMMENDED EXTERNAL COMPONENTS
1
14
256fs/384fs CLK
LRCIN
SCKI
FORMAT
DEEMPH
FROM AUDIO
PROCESSOR
2
DIN
13
12
3
BCKIN
4
NC
WM8725
11
10
9
NC
MUTE
VOUTL
VDD
10µF
+
5
CAP
ANALOGUE
ANALOGUE
OUTPUT FOR
LEFT
OUTPUT
FOR RIGHT
CHANNEL
External
LPF
External
LPF
6
7
VOUTR
GND
CHANNEL
8
GND
VDD
0.1µF
10µF
Figure 7 Recommended External Components
DETAIL OF RECOMMENDED EXTERNAL COMPONENTS SHOWING THE EXTERNAL
LOW PASS FILTER
External LPF
x2 for Stereo Operation
-
Filtered
Analogue
Output
VOUTR
VOUTL
1500pF
10k
+
10k
10k
680pF
100pF
Figure 8 Third-Order Low Pass Filter (LPF) Example
An external low pass filter is recommended (see Figure 8) if the device is driving a wideband
amplifier. In some applications, second-order or passive RC filter may be adequate.
PCB LAYOUT
1.
2.
3.
Place all supply decoupling capacitors as close as possible to their respective supply
pins and provide a low impedance path from the capacitors to the appropriate ground.
Separate analogue and digital ground planes should be situated under respective
analogue and digital device pins.
Avoid noise on the CAP reference pin. The decoupling capacitor should be placed as
close to this pin as possible with a low impedance path from the capacitor to analogue
ground.
4.
5.
Digital input signals should be screened from each other and from other sources of
noise to avoid cross-talk and interference. They should also run over the digital ground
plane to avoid introducing unwanted noise into the analogue ground plane.
Analogue output signal tracks should be kept as short as possible and over the
analogue ground plane reducing the possibility of losing signal quality.
PD ,Rev 4.3, February 2012
11
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
