WM8978 Wolfson Microelectronics Ltd., WM8978 Datasheet - Page 43

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WM8978

Manufacturer Part Number
WM8978
Description
The WM8978 is a low power, high quality stereo codec designed for portable applications such as Digital still camera or Digital Camcorde
Manufacturer
Wolfson Microelectronics Ltd.
Datasheet

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Preliminary Technical Data
Figure 21 DAC Digital Filter Path
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DIGITAL PLAYBACK (DAC) PATH
Table 22 DAC Enable Control
Table 23 DAC Control Register
The analogue outputs from the DACs can then be mixed with the aux analogue inputs and the ADC
analogue inputs. The mix is fed to the output drivers for headphone (LOUT1/ROUT1), speaker
(LOUT2/ROUT2) or line (OUT3/OUT4). OUT3 and OUT4 have additional mixers which allow them
to output different signals to the headphone and speaker outputs.
Digital data is passed to the WM8978 via the flexible audio interface and is then passed through a
variety of advanced digital filters (as shown in Figure 21) to the hi-fi DACs. The DACs are enabled
by the DACENL/R register bits.
The WM8978 also has a Soft Mute function, which, when enabled, gradually attenuates the volume
of the digital signal to zero. When disabled, the gain will ramp back up to the digital gain setting. This
function is enabled by default. To play back an audio signal, this function must first be disabled by
setting the SOFTMUTE bit to zero.
The digital audio data is converted to oversampled bit streams in the on-chip, true 24-bit digital
interpolation filters. The bitstream data enters the multi-bit, sigma-delta DACs, which convert it to a
high quality analogue audio signal. The multi-bit DAC architecture reduces high frequency noise and
sensitivity to clock jitter. It also uses a Dynamic Element Matching technique for high linearity and
low distortion.
R10
DAC Control
R3
Power
Management 3
REGISTER
ADDRESS
REGISTER
ADDRESS
BIT
0
1
0
1
2
3
6
BIT
DACPOLL
DACPOLR
AMUTE
DACOSR
SOFTMUTE
DACENL
DACENR
LABEL
LABEL
0
0
0
0
0
0
0
DEFAULT
DEFAULT
Left channel DAC enable
0 = DAC disabled
1 = DAC enabled
Right channel DAC enable
0 = DAC disabled
1 = DAC enabled
Left DAC output polarity:
0 = non-inverted
1 = inverted (180 degrees phase shift)
Right DAC output polarity:
0 = non-inverted
1 = inverted (180 degrees phase shift)
Automute enable
0 = Amute disabled
1 = Amute enabled
DAC oversampling rate:
0=64x (lowest power)
1=128x (best performance)
Softmute enable:
0=Enabled
1=Disabled
PTD Rev 2.6 November 2005
DESCRIPTION
DESCRIPTION
WM8978
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