Production Data
WM8750JL
OUTPUT SIGNAL PATH
The WM8750JL output signal paths consist of digital filters, DACs, analogue mixers and output
drivers. The digital filters and DACs are enabled when the WM8750JL is in ‘playback only’ or ‘record
and playback’ mode. The mixers and output drivers can be separately enabled by individual control
bits (see Analogue Outputs). Thus it is possible to utilise the analogue mixing and amplification
provided by the WM8750JL, irrespective of whether the DACs are running or not.
The WM8750JL receives digital input data on the DACDAT pin. The digital filter block processes the
data to provide the following functions:
Digital volume control
Graphic equaliser and Dynamic Bass Boost
Sigma-Delta Modulation
Two high performance sigma-delta audio DACs convert the digital data into two analogue signals (left
and right). These can then be mixed with analogue signals from the LINPUT1/2/3 and RINPUT1/2/3
pins, and the mix is fed to the output drivers, LOUT1/ROUT1, LOUT2/ROUT2, OUT3 and
MONOOUT.
LOUT1/ROUT1/OUT3: can drive a 16 or 32 stereo headphone or stereo line output.
LOUT2/ROUT2: can drive a 16 or 32 stereo headphone or stereo line output, or an
8 mono speaker.
MONOOUT: can drive a mono line output or other load down to 10k
DIGITAL DAC VOLUME CONTROL
The signal volume from each DAC can be controlled digitally, in the same way as the ADC volume
(see Digital ADC Volume Control). The gain and attenuation range is –127dB to 0dB in 0.5dB steps.
The level of attenuation for an eight-bit code X is given by:
0.5 (X-255) dB for 1 X 255;
MUTE for X = 0
The LDVU and RDVU control bits control the loading of digital volume control data. When LDVU or
RDVU are set to 0, the LDACVOL or RDACVOL control data is loaded into an intermediate register,
but the actual gain does not change. Both left and right gain settings are updated simultaneously
when either LDVU or RDVU are set to 1.
REGISTER
ADDRESS
BIT
LABEL
LDVU
DEFAULT
DESCRIPTION
R10 (0Ah)
8
0
Left DAC Volume Update
Left Channel
Digital Volume
0 = Store LDACVOL in intermediate
latch (no gain change)
1 = Update left and right channel
gains (left = LDACVOL, right =
intermediate latch)
7:0
LDACVOL
[7:0]
11111111
( 0dB )
Left DAC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -127dB
0000 0010 = -126.5dB
... 0.5dB steps up to
1111 1111 = 0dB
R11 (0Bh)
8
RDVU
0
Right DAC Volume Update
Right Channel
Digital Volume
0 = Store RDACVOL in intermediate
latch (no gain change)
1 = Update left and right channel
gains (left = intermediate latch, right
= RDACVOL)
7:0
RDACVOL
[7:0]
11111111
( 0dB )
Right DAC Digital Volume Control
similar to LDACVOL
Table 17 Digital Volume Control
PD, April 2012, Rev 4.1
27
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
