wm8982gefl-v Wolfson Microelectronics plc, wm8982gefl-v Datasheet - Page 29

• Manufacturer Part Number: wm8982gefl-v
• Description: Mono Codec With Speaker Driver And Video Buffer
• Manufacturer: Wolfson Microelectronics plc

Pre-Production
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NOTCH FILTER WORKED EXAMPLE
The following example illustrates how to calculate the a0 and a1 coefficients for a desired centre
frequency and -3dB bandwidth.
fc = 1000 Hz
fb = 100 Hz
fs = 48000 Hz
1.969995945
NFA0 = -a0 x 213 = -8085 (rounded to nearest whole number)
NFA1 = -a1 x 212 = 8069 (rounded to nearest whole number)
These values are then converted to a 2’s complement notation:
NfnA0[12:0] = 13’h1F95; Converting to 2’s complement NFA0 = 14’h4000 – 14’h1F95 = 14’h206B
NfnA1[12:0] = 13’h1F85; Converting to 2’s complement NFA0 = 14’h1F85
DIGITAL ADC VOLUME CONTROL
The output of the ADC can be digitally attenuated over a range from –127dB to 0dB in 0.5dB steps.
The gain for a given eight-bit code X is given by:
0.5 × (G-255) dB for 1 ≤ G ≤ 255;
Table 16 ADC Digital Volume Control
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a
a
R15
ADC Digital
Volume
1
0
0
b
REGISTER
ADDRESS
=
=
=
=
1
1
−
2
2
π
π
−
+
1 (
f
f
tan(
tan(
c
b
+
/
/
a
f
f
0
s
w
w
s
)
=
b
=
b
7:0
8
cos(
BIT
/
/
2
2
) 2
) 2
π
π
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x (100 / 48000) = 0.01308996939 rads
ADCVOL
[7:0]
ADCVU
x (1000 / 48000) = 0.1308996939 rads
=
0
1
1
)
LABEL
−
+
=
tan(
tan(
−
. 0
. 0
1 ( +
MUTE for G = 0
0130899693
0130899693
11111111
( 0dB )
Not
latched
DEFAULT
. 0
9869949627
ADC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -127dB
0000 0010 = -126.5dB
... 0.5dB steps up to
1111 1111 = 0dB
ADC volume does not update until a 1 is
written to ADCVU
/ 9
/ 9
) 2
) 2
)
= 0.9869949627
cos(
DESCRIPTION
PP, Rev 3.2, September 2008
. 0
1308996939
WM8982
)
=
29
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