WM8912
Production Data
DIGITAL-TO-ANALOGUE CONVERTER (DAC)
The WM8912 DACs receive digital input data from the DACDAT pin. The digital audio data is
converted to oversampled bit streams in the on-chip, true 24-bit digital interpolation filters. The
bitstream data enters two multi-bit, sigma-delta DACs, which convert them to high quality analogue
audio signals. The Wolfson SmartDAC™ architecture offers reduced power consumption, whilst also
delivering a reduction in high frequency noise and sensitivity to clock jitter. It also uses a Dynamic
Element Matching technique for high linearity and low distortion.
The analogue outputs from the DACs are sent directly to the output PGAs (see “Output Signal
Path”).
The DACs are enabled by the DACL_ENA and DACR_ENA register bits.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R18 (12h)
3
DACL_ENA
0
Left DAC Enable
Power
Management
6
0 = DAC disabled
1 = DAC enabled
Right DAC Enable
0 = DAC disabled
1 = DAC enabled
2
DACR_ENA
0
Table 15 DAC Enable Control
DAC DIGITAL VOLUME CONTROL
The output level of each DAC can be controlled digitally over a range from -71.625dB to 0dB in
0.375dB steps. The level of attenuation for an eight-bit code is detailed in Table 17.
The DAC_VU bit controls the loading of digital volume control data. When DAC_VU is set to 0, the
DACL_VOL or DACR_VOL control data is loaded into the respective control register, but does not
actually change the digital gain setting. Both left and right gain settings are updated when a 1 is
written to DAC_VU. This makes it possible to update the gain of both channels simultaneously.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R30 (1Eh)
8
DAC_VU
N/A
DAC Volume Update
DAC Digital
Volume Left
Writing a 1 to this bit causes left
and right DAC volume to be
updated simultaneously
7:0
DACL_VOL [7:0]
1100_0000
(0dB)
Left DAC Digital Volume
00h = Mute
01h = -71.625dB
02h = -71.250dB
… (0.375dB steps)
C0h to FFh = 0dB
(See Table 17 for volume range)
DAC Volume Update
R31 (1Fh)
8
DAC_VU
N/A
DAC Digital
Volume Right
Writing a 1 to this bit causes left
and right DAC volume to be
updated simultaneously
7:0
DACR_VOL [7:0]
1100_0000
(0dB)
Right DAC Digital Volume
00h = Mute
01h = -71.625dB
02h = -71.250dB
… (0.375dB steps)
C0h to FFh = 0dB
(See Table 17 for volume range)
Table 16 DAC Digital Volume Control
PD, Rev 4.0, September 2010
32
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
