wm8988 Wolfson Microelectronics plc, wm8988 Datasheet - Page 31

• Manufacturer Part Number: wm8988
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

Production Data
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ANALOGUE OUTPUTS
LOUT1/ROUT1 OUTPUTS
The LOUT1 and ROUT1 pins can drive a 16Ω or 32Ω headphone or a line output (see Headphone
Output and Line Output sections, respectively). The signal volume on LOUT1 and ROUT1 can be
independently adjusted under software control by writing to LOUT1VOL and ROUT1VOL,
respectively. Note that gains over 0dB may cause clipping if the signal is large. Any gain setting
below 0101111 (minimum) mutes the output driver. The corresponding output pin 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. If zero cross is enabled a timeout is
also available to update the gain if a zero cross does not occur. This function may be enabled by
setting TOEN in register R23 (17h).
Table 24 LOUT1/ROUT1 Volume Control
LOUT1/ROUT1 COMMON GROUND FEEDBACK (HPCOM)
The LOUT1/ROUT1 outputs also have the option of incorporating common ground feedback from the
output signal ground, via a connection to the HPCOM input. This common ground feedback signal
should be AC-coupled via a 4.7uF capacitor for the headphone loads. AC coupling of these outputs if
they are used as LINE level outputs requires similar 1 to 4.7uF AC coupling capacitors depending
upon LINE load resistance.
R2 (02h)
LOUT1
Volume
R3 (03h)
ROUT1
Volume
REGISTER
ADDRESS
8
7
6:0
8
7
6:0
BIT
LO1VU
LO1ZC
LOUT1VOL
[6:0]
RO1VU
RO1ZC
ROUT1VOL
[6:0]
LABEL
0
0
1111001
(0dB)
0
0
1111001
DEFAULT
Left Volume Update
0 = Store LOUT1VOL in intermediate
latch (no gain change)
1 = Update left and right channel gains
(left = LOUT1VOL, right =
intermediate latch)
Left zero cross enable
1 = Change gain on zero cross only
0 = Change gain immediately
LOUT1 Volume
1111111 = +6dB
… (80 steps)
0110000 = -67dB
0111111 to 0000000 = Analogue
MUTE
Right Volume Update
0 = Store ROUT1VOL in intermediate
latch (no gain change)
1 = Update left and right channel gains
(left = intermediate latch, right =
ROUT1VOL)
Right zero cross enable
1 = Change gain on zero cross only
0 = Change gain immediately
ROUT1 Volume
1111111 = +6dB
… (80 steps)
0110000 = -67dB
0111111 to 0000000 = Analogue
MUTE
DESCRIPTION
PD, Rev 4.0, October 2008
WM8988
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