WM8711 Wolfson Microelectronics Ltd., WM8711 Datasheet - Page 11

• Manufacturer Part Number: WM8711
• Description: Internet Audio DAC With Integrated Headphone Driver
• Manufacturer: Wolfson Microelectronics Ltd.

WM8711
WOLFSON MICROELECTRONICS LTD
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.
Table 2 DAC Software Control
DAC
The WM8711 employs a multi-bit sigma delta oversampling digital to analogue converter. The
scheme for the converter is illustrated in Figure 7.
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 WM8711 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 8. 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.
0000101
Digital Audio
Path Control
REGISTER
ADDRESS
FROM DAC
FILTERS
DIGITAL
2:1
3
BIT
DEEMP[1:0]
DACMU
LABEL
00
1
DEFAULT
TO LINE OUTPUT
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
PP Rev 1.2 November 2000
DESCRIPTION
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