Production Data
WM8750L
HEADPHONE SWITCH
The RINPUT3/HPDETECT pin can be used as a headphone switch control input to automatically
disable the speaker output and enable the headphone output e.g. when a headphone is plugged into
a jack socket. In this mode, enabled by setting HPSWEN, HPDETECT switches between headphone
and speaker outputs (e.g. when the pin is connected to a mechanical switch in the headphone socket
to detect plug-in). The HPSWPOL bit reverses the pin’s polarity. Note that the LOUT1, ROUT1,
LOUT2 and ROUT2 bits in register 26 must also be set for headphone and speaker output (see Table
31 and Table 32).
Note:
When RINPUT3/HPDETECT is used as the HPDETECT input, the thresholds become CMOS levels
(0.3 AVDD / 0.7 AVDD).
HPSWEN HPSWPOL HPDETECT L/ROUT1 L/ROUT2 Headphone
Speaker
enabled
no
(PIN23)
(reg. 26)
(reg. 26)
enabled
no
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
0
1
X
X
0
1
0
1
0
1
X
X
X
X
0
1
no
yes
no
yes
yes
no
yes
no
no
yes
no
no
yes
no
no
no
yes
no
no
no
no
yes
Table 31 Headphone Switch Operation
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R24 (18h)
HPSWEN
Headphone Switch Enable
6
0
Additional
Control (2)
0 : Headphone switch disabled
1 : Headphone switch enabled
Headphone Switch Polarity
HPSWPOL
5
0
0 : HPDETECT high = headphone
1 : HPDETECT high = speaker
Table 32 Headphone Switch
AVDD
HPSWEN = 1
HPSWPOL = 0
L/ROUT1 = L/ROUT2 = 1
-
-
ROUT1
LOUT1
L
R
33k
HPDETECT
Headphone/
speaker
switching
switch opens
with insertion
Figure 11 Example Headset Detection Circuit Using Normally-Open Switch
PD, Rev 4.4, August 2012
37
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
