wm8987 Wolfson Microelectronics plc, wm8987 Datasheet - Page 33

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

Production Data
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ANALOGUE OUTPUTS
ROUT1 OUTPUT
ROUT1 is the non-inverting left-channel output for BTL headsets (see page 54). It can drive 16Ω or
32Ω transducer loads. The ROUT1 signal volume can be adjusted under software control by writing
to ROUT1VOL. Note that gains over 0dB may cause clipping if the signal is large. Any gain setting
below 0101111 (minimum) mutes the output driver. The ROUT1 pin then remains at the same DC
level (the reference voltage on the VREF pin), so that no click noise is produced when muting or un-
muting.
A zero cross detect on the analogue output may also be enabled when changing the gain setting to
minimize audible clicks and zipper noise as the gain updates. A timeout is also available to update
the gain in the case that zero cross detection is enabled but no zero crossing occurs. This function
may be enabled by setting TOEN in register R23 (17h).
Table 25 ROUT1 Volume Control
LOUT2/ROUT2 OUTPUTS
LOUT2 and ROUT2 are analogue output pins similar to ROUT1. For BTL headsets, LOUT2 is the
non-inverting left output and ROUT2 the inverting right output (with ROUT2INV=1); for single-ended
headsets, LOUT2 is the left output and ROUT2 the right output.
R3 (03h)
ROUT1
Volume
R40 (28h)
LOUT2
Volume
REGISTER
REGISTER
ADDRESS
ADDRESS
8
7
6:0
6:0
7
8
BIT
BIT
RO1VU
RO1ZC
ROUT1VOL
[6:0]
LOUT2VOL
[6:0]
LO2ZC
LO2VU
LABEL
LABEL
0
0
1111001
1111001
(0dB)
0
0
DEFAULT
DEFAULT
ROUT1VOL Update
For any change to ROUT1VOL to take
effect, write ‘1’ to this bit.
Right zero cross enable
1 = Change gain on zero cross only
0 = Change gain immediately
ROUT1 Volume
1111111 = +6dB
… (80 steps)
0110000 = -67dB
0101111 to 0000000 = Analogue MUTE
LOUT2 volume
1111111 = +6dB
… (80 steps)
0110000 = -67dB
0101111 to 0000000 = Analogue MUTE
Left zero cross enable
1 = Change gain on zero cross only
0 = Change gain immediately
LOUT2 Volume Update
0 = Store LOUT2VOL in intermediate
1 = Update gain for both channels
latch (no gain change)
(left=LOUT2VOL, right=from
intermediate latch)
DESCRIPTION
DESCRIPTION
PD Rev 4.0 August 2008
WM8987L
33