Production Data
WM8750L
SPEAKER OUTPUT
LOUT2 and ROUT2 can differentially drive a mono 8 speaker as shown below.
LEFT
MIXER
LOUT2
LOUT2VOL
WM8750L
ROUT2INV = 1
VSPKR = L-(-R) = L+R
-1
ROUT2
RIGHT
MIXER
ROUT2VOL
Figure 14 Speaker Output Connection
The right channel is inverted by setting the ROUT2INV bit, so that the signal across the loudspeaker
is the sum of left and right channels.
LINE OUTPUT
The analogue outputs, LOUT1/ROUT1 and LOUT2/ROUT2, can be used as line outputs. Additionally,
OUT3 and MONOOUT can be used as a stereo line-out by setting OUT3SW=11 (reg. 24) and
ensuring the contents of registers 38 and 39 (mono-out mix) are the same as reg. 34 and 35 (left out
mix). Recommended external components are shown below.
C1
R1
1uF
100 Ohm
LOUT1/2
or OUT3 (OUT3SW=11)
LINE-OUT
SOCKET
(LEFT)
AGND
AGND
WM8750L
ROUT1/2
or MONOOUT
LINE-OUT
SOCKET
(RIGHT)
C2
1uF
R2
100 Ohm
Figure 15 Recommended Circuit for Line Output
The DC blocking capacitors and the load resistance together determine the lower cut-off frequency, fc.
Assuming a 10 kOhm load and C1, C2 = 1F:
fc = 1 / 2 (RL+R1) C1 = 1 / (2 x 10.1k x 1F) = 16 Hz
Increasing the capacitance lowers fc, improving the bass response. Smaller values of C1 and C2 will
diminish the bass response. The function of R1 and R2 is to protect the line outputs from damage
when used improperly.
PD, Rev 4.4, August 2012
39
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
