WM8731SEDSSLASHR datasheet(27/63 Pages) WOLFSON

27 / 63 page

WM8731 / WM8731L

Production Data

PD Rev 4.3 August 2006

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.

FROM DIGITAL

AUDIO

INTERFACE

MUTE

DIGITAL

INTERPOLATION

FILTER

TO LINE

OUTPUTS

DIGITAL

DE_EMPHASIS

DEEMP

DACMU

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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

2:1

DEEMP[1:0]

De-emphasis Control

(Digital)

11 = 48kHz

10 = 44.1kHz

01 = 32kHz

00 = Disable

0000101

Digital

Audio Path

Control

DACMU

DAC Soft Mute Control

(Digital)

1 = Enable soft mute

0 = Disable soft mute

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.

FROM DAC

DIGITAL

FILTERS

TO LINE OUTPUT

Figure 18 Multi-Bit Oversampling Sigma Delta Schematic

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