WM8955BL
Production Data
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 gain) 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.
The analogue outputs have a zero cross detect feature to minimize audible clicks and zipper noise
when on gain changes (i.e. the updating of the gain value is delayed until the signal passes through
zero). By default, this includes a time-out function, which forces the gain to update if no zero crossing
occurs within a certain period of time.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R2 (02h)
LOUT1
Volume
6:0
LOUT1VOL
1111001
(0dB)
LOUT1 Volume
1111111 = +6dB
… (80 steps)
0110000 = -67dB
0101111 to 0000000 = Analogue MUTE
LOUT1 zero cross enable
1 = Change gain on zero cross only
0 = Change gain immediately
Left Volume Update
7
LO1ZC
LO1VU
0
0
8
0 = Store LOUT1VOL in intermediate
latch (no gain change)
1 = Update left and right channel gains
(left = LOUT1VOL, right =
intermediate latch)
R3 (03h)
ROUT1
Volume
6:0
7
ROUT1VOL
RO1ZC
1111001
(0dB)
0
ROUT1 Volume
Similar to LOUT1VOL
ROUT1 zero cross enable
Similar to LO1ZC
8
RO1VU
0
Right Volume Update
0 = Store ROUT1VOL in intermediate
latch (no gain change)
1 = Update left and right channel gains
(left = intermediate latch, right =
ROUT1VOL)
R23 (17h)
0
TOEN
1
Time-out enable for zero-cross detectors
0 = time-out disabled (i.e. gains are
never updated if there is no zero
crossing)
1 = time-out enabled
Table 14 LOUT1/ROUT1 Volume Control
PD Rev 4.1 February 2007
24
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
