wm8987 Wolfson Microelectronics plc, wm8987 Datasheet - Page 28

• Manufacturer Part Number: wm8987
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8987L
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OUTPUT SIGNAL PATH
The WM8987L output signal paths consist of digital filters, DACs, analogue mixers and output
drivers. The digital filters and DACs are enabled when the WM8987L 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 WM8987L, irrespective of whether the DACs are running or not.
The WM8987L receives digital input data on the DACDAT pin. The digital filter block processes the
data to provide the following functions:
•
•
•
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 L/RINPUT1 and L/RINPUT2
pins, and the mix is fed to the output drivers, ROUT1, LOUT2/ROUT2 and OUT3.
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;
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.
Table 17 Digital Volume Control
R10 (0Ah)
Left Channel
Digital Volume
R11 (0Bh)
Right Channel
Digital Volume
REGISTER
ADDRESS
Digital volume control
Graphic equaliser and Dynamic Bass Boost
Sigma-Delta Modulation
8
7:0
8
7:0
BIT
LDVU
LDACVOL
[7:0]
RDVU
RDACVOL
[7:0]
LABEL
MUTE for X = 0
0
11111111
( 0dB )
0
11111111
( 0dB )
DEFAULT
Left DAC Volume Update
0 = Store LDACVOL in intermediate
latch (no gain change)
1 = Update left and right channel
gains (left = LDACVOL, right =
intermediate latch)
Left DAC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -127dB
0000 0010 = -126.5dB
... 0.5dB steps up to
1111 1111 = 0dB
Right DAC Volume Update
0 = Store RDACVOL in intermediate
latch (no gain change)
1 = Update left and right channel
gains (left = intermediate latch, right
= RDACVOL)
Right DAC Digital Volume Control
similar to LDACVOL
DESCRIPTION
PD Rev 4.0 August 2008
Production Data
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