wm8987 Wolfson Microelectronics plc, wm8987 Datasheet - Page 55

• Manufacturer Part Number: wm8987
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

Production Data
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Figure 47 Driving single-ended headphones using DC-blocking capacitors
It requires the following register settings:
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•
•
•
•
This method for driving a headphone requires two capacitors in the LOUT2 and ROUT2 paths. Their
capacitance C and the load resistance R together determine the lower cut-off frequency, f
Increasing R or C lowers f
the bass response. For example, assuming a 16 Ohm load and C = 220µF:
f
CAPLESS DRIVE
To drive single-ended headphones without DC blocking capacitors, the analogue outputs should be
used as follows:
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•
•
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This setup is illustrated in Figure 47.
c
= 1 / 2π R
Set only the LOUT2 and ROUT2 bits in R26 to ‘1’ to enable LOUT2, ROUT2 and the
associated mixers. The ROUT1, MONO and OUT3 bits should remain at ‘0’.
Set LD2LO (R34) and RD2RO (R37) to ‘1’ to enable the correct audio paths (in the case
of audio playback from an analogue source, select the input pin using LMIXSEL and
RMIXSEL, and set LI2LO/RI2RO instead of LD2LO/RD2RO).
Leave ROUT2INV = 0 in R24, so that the right-channel signal going to ROUT2 is not
inverted.
The left channel volume is controlled by LOUT2VOL.
The right channel volume is controlled by ROUT2VOL.
LOUT2 is the left output
ROUT2 is the right output
OUT3 is a pseudo-ground output for the headphone
ROUT1 is unused and should be disabled
L
C
1
= 1 / (2π x 16Ω x 220µF) = 45 Hz
c
, improving the bass response. Smaller capacitance values will diminish
PD Rev 4.0 August 2008
WM8987L
55
c
.