WM8731L WOLFSON [Wolfson Microelectronics plc], WM8731L Datasheet - Page 27

• Manufacturer Part Number: WM8731L
• Description: Portable Internet Audio CODEC with Headphone Driver and Programmable Sample Rates
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

WM8731 / WM8731L
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There are several types of ADC filters, frequency and phase responses of these are shown in Digital
Filter Characteristics. The filter types are automatically configured depending on the sample rate
chosen. Refer to the sample rate section for more details.
DAC FILTERS
The DAC filters perform true 24 bit signal processing to convert the incoming digital audio data from
the digital audio interface at the specified sample rate to multi-bit oversampled data for processing by
the analogue DAC. Figure 17 illustrates the DAC digital filter path.
Figure 17 DAC Filter Schematic
The DAC digital filter can apply digital de-emphasis under software control, as shown in Table 7.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 7 DAC Software Control
DAC
The WM8731/L employs a multi-bit sigma delta oversampling digital to analogue converter. The
scheme for the converter is illustrated in Figure 18.
Figure 18 Multi-Bit Oversampling Sigma Delta Schematic
0000101
Digital
Audio Path
Control
REGISTER
ADDRESS
FROM DIGITAL
INTERFACE
FROM DAC
AUDIO
FILTERS
DIGITAL
2:1
3
BIT
DE_EMPHASIS
DEEMP
DIGITAL
DEEMP[1:0]
DACMU
LABEL
DACMU
MUTE
00
1
DEFAULT
INTERPOLATION
DIGITAL
FILTER
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
PD Rev 4.3 August 2006
DESCRIPTION
OUTPUTS
TO LINE
Production Data
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