wm8952 Wolfson Microelectronics plc, wm8952 Datasheet - Page 25

• Manufacturer Part Number: wm8952
• Description: Mono Adc With Microphone Pre-amplifier
• Manufacturer: Wolfson Microelectronics plc

Pre Production
w
DIGITAL ADC VOLUME CONTROL
Table 19 ADC Volume
The notch filter coefficients are calculated as follows:
Where:
The actual register values can be determined from the coefficients as follows:
NFn_A0 = -a0 x 2
NFn_A1 = -a1 x 2
These values are then converted to a 14-bit sign / magnitude notation.
To configure Notch Filter 3 as a 1
coefficients as follows:
Where:
The actual register values can be determined from the coefficients as follows:
These values are then converted to a 14-bit sign / magnitude notation.
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
a
a
a
w
R15
ADC Digital
Volume
1
0
0
c
=
=
=
REGISTER
ADDRESS
=
0
tan(
tan(
1
1
2
−
+
π
f
tan(
tan(
c
w
w
f
f
NF3_A0 = 0
NF3_A1 = -a
w
w
f /
c
c
c
c
= centre frequency in Hz, f
s
= cut-off frequency in Hz, f
0
b
w
w
/
/
) 2
) 2
=
=
b
b
2
2
/
/
−
+
) 2
) 2
π
π
13
12
1
1
f
f
c
b
7:0
BIT
f /
f /
s
s
1
x2
12
ADCVOL
[7:0]
LABEL
st
order low pass filter, set the NF3_LP bit to 1 and calculate the
b
s
= -3dB bandwidth in Hz, f
= sample frequency in Hz
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
PP, Rev 3.0, December 2008
WM8952
25