wm8940gefl-v Wolfson Microelectronics plc, wm8940gefl-v Datasheet - Page 27

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wm8940gefl-v

Manufacturer Part Number
wm8940gefl-v
Description
Mono Codec With Speaker Driver
Manufacturer
Wolfson Microelectronics plc
Datasheet
w
Production Data
DIGITAL ADC VOLUME CONTROL
Table 19 ADC Volume
Where:
The actual register values can be determined from the coefficients as follows:
To configure Notch Filter 3 as a 1
coefficients as follows:
Where:
The actual register values can be determined from the coefficients as follows:
The output of the ADCs 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:
Gain = 0.5 x (x–255) dB for 1 ≤ x ≤ 255, MUTE for x = 0
R15
ADC Digital
Volume
REGISTER
ADDRESS
f
NFn_A0 = -a0 x 2
NFn_A1 = -a1 x 2
f
NF3_A0 = 0
NF3_A1 = -a
a
a
w
w
a
a
w
c
c
= centre frequency in Hz, f
= cutoff frequency in Hz, f
1
1
0
0
0
b
c
=
=
=
=
=
=
=
1
1
0
tan(
tan(
2
2
2 π
π
π
7:0
1 (
+
BIT
f
f
f
tan(
tan(
c
b
c
+
w
w
1
/
/
/
x2
c
c
a
f
f
f
12
ADCVOL
[7:0]
/
0
/
w
w
s
s
13
12
s
)
) 2
) 2
b
b
cos(
LABEL
/
/
+
) 2
) 2
1
1
st
w
order low pass filter, set the NF3_LP bit to 1 and calculate the
0
b
s
)
= sample frequency in Hz
= -3dB bandwidth in Hz, f
11111111
( 0dB )
DEFAULT
ADC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -127dB
0000 0010 = -126.5dB
... 0.5dB steps up to
1111 1111 = 0dB
s
= sample frequency in Hz
DESCRIPTION
PD, Rev 4.2, April 2008
WM8940
27

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