Production Data
WM9715L
BTL LOUDSPEAKER OUTPUT
LOUT2 and ROUT2 can differentially drive a mono 8Ω loudspeaker as shown below.
Figure 27 Speaker Output Connection (INV = 1)
The right channel is inverted by setting the INV bit, so that the signal across the loudspeaker is the
sum of left and right channels.
COMBINED STEREO HEADSET / BTL EAR SPEAKER
In smartphone applications with a loudspeaker and separate ear speaker (receiver), a BTL ear
speaker can be connected at the OUT3 pin, as shown below.
Figure 28 Combined Headset / BTL Ear Speaker (OUT3SRC = 00)
The ear speaker and the stereo headset play the same signal. Whenever the headset is plugged in,
the headphone outputs are enabled and OUT3 disabled. When the headset is not plugged in, OUT3
is enabled. This requires the use of a headset jack with a built-in mechanical switch, connected to a
GPIO pin on the system CPU. Depending on the state of the switch, the GPIO pin is either grounded
or high (due to a pull-up resistor). Whenever the CPU detects a change in the GPIO logic level, it
should update the WM9715L registers to enable / disable the appropriate analogue outputs.
COMBINED HEADSET / SINGLE-ENDED EAR SPEAKER
Instead of a BTL ear speaker, a single-ended ear speaker can also be used, as shown below.
Figure 29 Combined Headset / Single-ended Ear Speaker (OUT3SRC = 01)
PD Rev 4.0 December 2007
75
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
