WM8978 Datasheet, PDF (48/78 Pages) Wolfson Microelectronics plc – STEREO CODEC WITH SPEAKER DRIVER

WM8978
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REGISTER
ADDRESS
R56
OUT3 mixer
control
BIT
LABEL
6
OUT3MUTE
3
OUT4_2OUT3
2
BYPL2OUT3
1
LMIX2OUT3
0
LDAC2OUT3
R57
6
OUT4 mixer
control
5
4
OUT4MUTE
HALFSIG
LMIX2OUT4
3
LDAC2OUT4
2
BYPR2OUT4
1
RMIX2OUT4
0
RDAC2OUT4
Table 37 OUT3/OUT4 Mixer Registers
DEFAULT
0
0
0
0
1
0
0
0
0
0
0
1
DESCRIPTION
0 = Output stage outputs OUT3 mixer
1 = Output stage muted – drives out
VMID. Can be used as VMID buffer in
this mode.
OUT4 mixer output to OUT3
0 = disabled
1= enabled
Left ADC input to OUT3
0 = disabled
1= enabled
Left DAC mixer to OUT3
0 = disabled
1= enabled
Left DAC output to OUT3
0 = disabled
1= enabled
0 = Output stage outputs OUT4 mixer
1 = Output stage muted – drives out
VMID. Can be used as VMID buffer in
this mode.
0 = OUT4 normal output
1 = OUT4 attenuated by 6dB
Left DAC mixer to OUT4
0 = disabled
1= enabled
Left DAC to OUT4
0 = disabled
1= enabled
Right ADC input to OUT4
0 = disabled
1= enabled
Right DAC mixer to OUT4
0 = disabled
1= enabled
Right DAC output to OUT4
0 = disabled
1= enabled
The OUT3 and OUT4 output stages each 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 20, 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 33 summarises the effect of the OUT3BOOST
and OUT4BOOST control bits.
w
PP Rev 1.7 January 2005
48