wm8940gefl-v Wolfson Microelectronics plc, wm8940gefl-v Datasheet - Page 25

• Manufacturer Part Number: wm8940gefl-v
• Description: Mono Codec With Speaker Driver
• Manufacturer: Wolfson Microelectronics plc

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Production Data
Figure 11 Labelling of Notch Filters and Arrangement of Notch Filter Enables
Table 14 High Pass Filter Cut-off Frequencies (HPFAPP=1)
PROGRAMMABLE NOTCH FILTERS
Table 15 Notch Filter 0 Function
Note that the High Pass filter values (when HPFAPP=1) work on the basis that the SR register bits
are set correctly for the actual sample rate as shown in Table 14.
Four programmable notch filters are provided. These filters have a programmable centre frequency
and bandwidth, programmable via two coefficients, a0 and a1. a0 and a1 are represented by the
register bits NFx_A0[13:0] and NFx_A1[13:0]. Notch Filter 3 can also be programmed as a 1
low pass filter.
Because these coefficient values require two register writes to set up there is an NFx_UP (Notch
Filter Update) flag for each filter which should be set only when both A0 and A1 for the filter have
been set.
The notch filters can be individually enabled, using the corresponding NFx_EN register bit, as can be
seen in Figure 11.
The notch filter coefficients must be entered using a sign / magnitude notation.
HPFCUT
000
001
010
011
100
101
110
111
R16
Notch Filter 0A
R17
Notch Filter 0B
REGISTER
ADDRESS
102
131
163
204
261
327
408
82
8
15
14
13:0
15
13:0
SR=101/100
BIT
11.025
113
141
180
225
281
360
450
563
NF0_UP
NF0_EN
NF0_A0
NF0_UP
NF0_A1
LABEL
122
153
196
245
306
392
490
612
12
102
131
163
204
261
327
408
16
82
0
0
0
0
0
DEFAULT
SR=011/010
FS (KHZ)
22.05
113
141
180
225
281
360
450
563
Notch filter 0 update. The notch filter 0
values used internally only update when
one of the NF0_UP bits is set high.
Notch filter 0 enable:
0=Disabled
1=Enabled
Notch Filter 0 a0 coefficient
Notch filter 0 update. The notch filter 0
values used internally only update when
one of the NF0_UP bits is set high.
Notch Filter 0 a1 coefficient
122
153
196
245
306
392
490
612
24
102
131
163
204
261
327
408
32
82
DESCRIPTION
SR=001/000
PD, Rev 4.2, April 2008
44.1
113
141
180
225
281
360
450
563
122
153
196
245
306
392
490
612
WM8940
48
st
order
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