Production Data
WM8741
NORMAL PCM MODE DIGITAL FILTER SELECTION
The WM8741 has a number of advanced digital filters that can be selected in all PCM operation
modes (with the exception of 8FS mode).
REGISTER ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
Selects FIR1 filter response
000 = Response 1
R6
Filter Control
06h
[2:0] FIRSEL
000
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. A summary of the filter characteristics is given in Table 39 below:
OSR
RESPONSE
NOTES
Low
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
Linear phase half-band filter for backward compatibility
Minimum phase ‘soft-knee’ filter
Minimum phase half-band filter
Linear phase apodising filter
Minimum phase apodising filter
Linear phase ‘soft-knee’ filter
Minimum phase ‘soft-knee’ filter
Linear phase ‘brickwall’ filter
Minimum phase apodising filter
Linear phase apodising filter
Linear phase ‘soft-knee’ filter
Minimum phase ‘soft-knee’ filter
Linear phase ‘brickwall’ filter
Minimum phase apodising filter
Linear phase apodising filter
Medium
High
Table 39 PCM Digital Filter Summary
For full details of the filter characteristics available in normal PCM mode, please see Table 64 to
Table 66 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 67 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.
REGISTER ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R6
Filter Control
06h
[4:3] DSDFILT
[1:0]
00
Selects Compensation Filter
response
00 = Response 1
01 = Response 2
10 = Response 3
11 = Response 4
Table 40 DSD Plus Digital Filter Selection
PD, Rev 4.2, October 2009
37
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
