WM8956 Datasheet, PDF (25/80 Pages) Cirrus Logic – Hi-Fi DAC with 1W Stereo Class D Speaker Drivers

Production Data
WM8956
OUTPUT SIGNAL PATH
The hi-fi DACs and DAC digital filters are enabled by register bits DACL and DACR. 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 WM8956, irrespective of
whether the DACs are enabled or not.
The WM8956 DACs receive digital input data on the DACDAT pin. The digital filter block processes
the data to provide the following functions:
 Digital volume control with soft mute and soft un-mute
 Mono mix
 3D stereo enhancement
 De-emphasis
 Sigma-delta modulation
High performance sigma-delta 24-bit audio DAC converts the digital data into an analogue signal.
The analogue outputs from the DACs can then be mixed with the analogue line inputs. This mix is fed
to the output drivers for headphone or speaker output. OUT3 can provide a mono mix of left and right
mixers or a pseudo-ground for capless headphone drive.
DIGITAL PLAYBACK (DAC) PATH
Digital data is passed to the WM8956 via the flexible audio interface to the hi-fi DACs. The DACs are
enabled by the DACL and DACR register bits.
REGISTER
ADDRESS
R26 (1Ah)
Power
Management (2)
BIT LABEL
8
DACL
7
DACR
Table 8 DAC Enable Control
DEFAULT
DESCRIPTION
0
Left Channel DAC Enable
0 = DAC disabled
1 = DAC enabled
0
Right Channel DAC Enable
0 = DAC disabled
1 = DAC enabled
DIGITAL DAC VOLUME CONTROL
The signal volume from each DAC can be controlled digitally. 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 DACVU control bit controls the loading of digital volume control data. When DACVU is 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 DACVU is set to
1.
See "Volume Updates" for more information on volume update bits.
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PD, November 2011, Rev 4.1
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