WM8955L
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ANALOGUE OUTPUTS
ENABLING THE OUTPUTS
Each analogue output of the WM8955L can be separatelyenabled or disabled. The analogue mixer
associated with each output is powered on or off along with the output pin. All outputs are disabled by
default. To save power, unused outputs should remain disabled.
Outputs can be enabled at anytime, except when the WM8955L is in OFF mode, as this maycause
pop noise (see Minimising Pop Noise at the Analogue Outputs)
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R26 (1Ah)
8
7
5
4
2
LOUT1
0
0
0
0
0
0
LOUT1 Enable
Power
Management
(2)
ROUT1
LOUT2
ROUT2
MONO
OUT3
ROUT1 Enable
LOUT2 Enable
ROUT2 Enable
MONOOUT Enable
OUT3 Enable
1
Note: All “Enable” bits are 1 = ON, 0 = OFF
Table 10 Analogue Output Control
HEADPHONE SWITCH
The HPDETECT pin can be used as a headphone switch control input to automaticallydisable the
speaker output and enable the headphone output e.g. when a headphone is plugged into a jack
socket. In this mode, enabled bysetting HPSWEN, HPDETECT switches between headphone and
speaker outputs (typically, the pin is connected to a mechanical switch in the headphone socket to
detect plug-in). The HPSWPOL bit reverses the pin’s polarity. HPDETECT has CMOS thresholds at
0.3 AVDD / 0.7 AVDD. Note that the LOUT1, ROUT1, LOUT2 and ROUT2 bits in register 26 must
also be set to enable headphone and speaker outputs (see tables below).
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R24 (18h)
6
HPSWEN
0
0
Headphone Switch Enable
Additional (1)
0 : Headphone switch disabled
1 : Headphone switch enabled
Headphone Switch Polarity
5
HPSWPOL
0 : HPDETECT high = headphone
1 : HPDETECT high = speaker
Table 11 Headphone Switch
HPSWEN HPSWPOL HPDETECT L/ROUT1 L/ROUT2 Headphone
Speaker
(PIN23)
(reg. 26)
(reg. 26)
enabled
no
enabled
0
0
0
0
1
1
1
1
1
1
1
1
X
X
X
X
0
0
0
0
1
1
1
1
X
X
X
X
0
0
1
1
0
0
1
1
0
0
1
1
X
X
0
1
X
X
0
1
0
1
0
1
0
1
X
X
0
1
X
X
no
y
no
es
es
yes
yes
no
no
yes
no
y
no
no
no
no
no
no
no
y
yes
no
yes
no
no
es
Table 12 Headphone Switch Operation
Product Preview Rev 0.4 May2003
22
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
