WM8721(2000) Ver la hoja de datos (PDF) - Wolfson Microelectronics plc
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WM8721 Datasheet PDF : 34 Pages
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WM8721
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The DAC digital filter can apply digital de-emphasis under software control, as shown in Table 2. The
DAC can also perform a soft mute where the audio data is digitally brought to a mute level. This
removes any abrupt step changes in the audio that might otherwise result in audible clicks in the
audio outputs.
REGISTER
ADDRESS
0000101
Digital Audio
Path Control
BIT
2:1
LABEL
DEEMP[1:0]
DEFAULT
00
3
DACMU
1
Table 2 DAC Software Control
DESCRIPTION
De-emphasis Control
(Digital)
11 = 48KHz
10 = 44.1KHz
01 = 32KHz
00 = Disable
DAC Soft Mute Control
(Digital)
1 = Enable soft mute
0 = Disable soft mute
DAC
The WM8721 employs a multi-bit sigma delta oversampling digital to analogue converter. The
scheme for the converter is illustrated Figure 7.
FROM DAC
DIGITAL
FILTERS
TO LINE OUTPUT
Figure 7 Multi-Bit Oversampling Sigma Delta Schematic
The DAC converts the multi-level digital audio data stream from the DAC digital filters into high
quality analogue audio.
LINE OUTPUTS
The WM8721 provides two low impedance line outputs LLINEOUT and RLINEOUT, suitable for
driving typical line loads of impedance 10K and capacitance 50pF.
The LLINEOUT and RLINEOUT outputs are only available at a line output level and are not level
adjustable in the analogue domain, having a fixed gain of 0dB. The level is fixed such that at the DAC
full scale level the output level is Vrms at AVDD = 3.3 volts. Note that the DAC full scale level tracks
directly with AVDD. The scheme is shown in Figure 9. The line output includes a low order audio low
pass filter for removing out-of band components from the sigma-delta DAC. Therefore no further
external filtering is required in most applications.
WOLFSON MICROELECTRONICS LTD
PP Rev 1.3 November 2000
11
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