WM8741 datasheet(38/63 Pages) WOLFSON

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WM8741

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PP Rev 1.3 October 2007

NORMAL PCM MODE DIGITAL FILTER SELECTION

The 8741 has a number of advanced digital filters that can be selected in all PCM operation modes

(with the exception of 8FS mode).

BIT

LABEL

DEFAULT

DESCRIPTION

Filter Control

06h

[2:0]

FIRSEL

000

Selects FIR1 filter response

000 = Response 1

001 = Response 2

010 = Response 3

011 = Response 4

100 = Response 5

Table 38 PCM Advanced Digital Filter Selection

Five digital filters are available for selection in each of the three OSR modes (low, medium and high

rate) as selected by the OSR bit described in Table 20. It is recommended that the device is muted

before the filter response is changed to prevent noise as the filters are reset from appearing on the

outputs.

For full details of the filter characteristics available in normal PCM mode, please see Table 61 to

Table 63 and Figure 28 to Figure 57.

8FS MODE DIGITAL FILTER

In 8FS mode, the majority of the internal filters are bypassed. In this mode, the data is filtered using

only the filter characteristic described by Table 64 and shown in Figure 58 and Figure 59.

DSD PLUS FILTER SELECTION

The WM8741 has a number of compensation filters that can be selected in DSD Plus mode.

BIT

LABEL

DEFAULT

DESCRIPTION

Filter Control

06h

[4:3]

DSDFILT

[1:0]

Selects Compensation Filter

response

00 = Response 1

01 = Response 2

10 = Response 3

11 = Response 4

Table 39 DSD Plus Digital Filter Selection

It is recommended that the device is muted before the filter response is changed to prevent noise as

the filters are reset from appearing on the outputs.

Full details of these filters are described in Table 65 and Figure 60 to Figure 67.

DSD DIRECT DIGITAL FILTER

The DSD Direct filter has been designed to provide the minimal of processing to the data with no

decimation, re-quantisation or noise-shaping, in order to preserve the signal integrity as much as

possible.

As a result the filter has a wide bandwidth and a very gradual attenuation.

It is

recommended that this filter is augmented by analogue post-DAC filtering in order to adhere to the

Scarlet-Book SACD standard.

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