wm8903 Wolfson Microelectronics plc, wm8903 Datasheet - Page 51

• Manufacturer Part Number: wm8903
• Description: Ultra Low Power Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

Pre-Production
DIGITAL-TO-ANALOGUE CONVERTER (DAC)
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The WM8903 DACs receive digital input data from the DACDAT pin and via the digital sidetone path
(see “Digital Mixing” section). 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 can then be mixed with other analogue inputs before being
sent to the analogue output pins (see “Output Signal Path”).
The DACs are enabled by the DACL_ENA and DACR_ENA register bits.
Table 26 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 X is given by:
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.
Table 27 DAC Digital Volume Control
R18 (12h)
Power
Management
6
R30 (1Eh)
DAC Digital
Volume Left
R31 (1Fh)
DAC Digital
Volume Right
REGISTER
REGISTER
ADDRESS
ADDRESS
MUTE for X = 0
DAC gain = 0.375 × (X-192) dB for 1 ≤ X ≤ 192
DAC gain = 0dB for 192 ≤ X ≤ 255
BIT
BIT
7:0
7:0
3
2
8
8
DACL_ENA
DACR_ENA
DACVU
DACL_VOL [7:0]
DACVU
DACR_VOL [7:0]
LABEL
LABEL
1100_0000
1100_0000
DEFAULT
DEFAULT
(0dB)
(0dB)
N/A
N/A
0
0
Left DAC Enable
0 = DAC disabled
1 = DAC enabled
Right DAC Enable
0 = DAC disabled
1 = DAC enabled
DAC Volume Update
Writing a 1 to this bit causes left
and right DAC volume to be
updated simultaneously
Left DAC Digital Volume
(See Table 28 for volume range)
DAC Volume Update
Writing a 1 to this bit causes left
and right DAC volume to be
updated simultaneously
Right DAC Digital Volume
(See Table 28 for volume range)
PP, Rev 3.1, August 2009
DESCRIPTION
DESCRIPTION
WM8903
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