WM8976
Pre-Production
REGISTER
ADDRESS
BIT
LABEL
LOUT2ZC
DEFAULT
DESCRIPTION
R54
7
0
Speaker volume zero cross enable:
1 = Change gain on zero cross only
0 = Change gain immediately
Left speaker output mute:
0 = Normal operation
1 = Mute
LOUT2 (SPK)
Volume
control
6
LOUT2MUTE
LOUT2VOL
0
5:0
111001
Left speaker output volume:
000000 = -57dB
...
111001 = 0dB
...
111111 = +6dB
8
7
SPKVU
Not latched LOUT2 and ROUT2 volumes do not
update until a 1 is written to SPKVU
(in reg 54 or 55)
R55
ROUT2ZC
0
Speaker volume zero cross enable:
1 = Change gain on zero cross only
0 = Change gain immediately
Right speaker output mute:
0 = Normal operation
1 = Mute
ROUT2 (SPK)
Volume
control
6
ROUT2MUTE
ROUT2VOL
0
5:0
111001
Right speaker output volume:
000000 = -57dB
...
111001 = 0dB
...
111111 = +6dB
8
SPKVU
Not latched LOUT2 and ROUT2 volumes do not
update until a 1 is written to SPKVU
(in reg 54 or 55)
Table 40 Speaker Volume Control
The signal output on LOUT2/ROUT2 comes from the Left/Right Mixer circuits and can be any
combination of the DAC output, the Bypass path (output of the input boost stage) and the AUX input.
The LOUT2/ROUT2 volume is controlled by the LOUT2VOL/ ROUT2VOL register bits. Gains over
0dB may cause clipping if the signal is large. The LOUT2MUTE/ ROUT2MUTE register bits cause
the speaker outputs to be muted (the output DC level is driven out). The output pins remain at the
same DC level (DCOP), so that no click noise is produced when muting or un-muting
The speaker output stages also have a selectable gain boost of 1.5x (3.52dB). When this boost is
enabled the output DC level is also level shifted (from AVDD/2 to 1.5xAVDD/2) to prevent the signal
from clipping. A dedicated amplifier BUFDCOP, as shown in Figure 23, is used to perform the DC
level shift operation. This buffer must be enabled using the BUFDCOPEN register bit for this
operating mode. It should also be noted that if SPKVDD is not equal to or greater than 1.5xAVDD
this boost mode may result in signals clipping. Table 42 summarises the effect of the SPKBOOST
control bits.
PP Rev 3.0 April 2006
54
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
