WM8955BL Wolfson Microelectronics, WM8955BL Datasheet - Page 41

• Manufacturer Part Number: WM8955BL
• Description: Stereo DAC
• Manufacturer: Wolfson Microelectronics

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Production Data
MINIMISING POP NOISE AT THE ANALOGUE OUTPUTS
LINE OUTPUT CONFIGURATION
To minimise any pop or click noise when the system is powered up or down, the following procedures
are recommended.
POWER UP
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POWER DOWN
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All the analogue outputs, LOUT1/ROUT1, LOUT2/ROUT2, and MONOOUT, can be used as line
outputs. Recommended external components are shown below.
Figure 29 Recommended Circuit for Line Output
The DC blocking capacitors and the load resistance together determine the lower cut-off frequency, f
Assuming a 10 kΩ load and C1, C2 = 1μF:
f
Increasing the capacitance lowers f
diminish the bass response. The function of R1 and R2 is to protect the line outputs from damage
when used improperly.
c
= 1 / 2π (R
Switch on power supplies. By default the WM8955BL is in OFF Mode (i.e. only the control
interface is powered up)
Enable the reference voltage VREF by setting the WM8955BL to Standby mode. DO NOT
enable any of the analogue outputs at this point.
Allow VREF to settle. The settling time depends on the value of the capacitor connected at
VMID, and the size of the resistors selected using VMIDSEL (τ = RC).
Enable DACs, etc. as required.
Enable outputs required.
Set DACMU = 0 to soft-un-mute the audio DACs.
Set DACMU = 1 to soft-mute the audio DACs.
Disable outputs.
Switch off the power supplies.
WM8955BL
L
+R
1
) C
ROUT2
LOUT2
1
= 1 / (2π x 10.1kΩ x 1μF) = 16 Hz
1uF
1uF
C1
C2
100 Ohm
100 Ohm
c
R1
R2
, improving the bass response. Smaller values of C1 and C2 will
AGND
AGND
LINE-OUT SOCKET
LINE-OUT SOCKET
(RIGHT)
(LEFT)
PD Rev 4.1 February 2007
WM8955BL
41
c
.