WM8980CGEFL/RV WOLFSON [Wolfson Microelectronics plc], WM8980CGEFL/RV Datasheet - Page 34

• Manufacturer Part Number: WM8980CGEFL/RV
• Description: Stereo CODEC with Speaker Driver and Video Buffer
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

WM8980
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DIGITAL ADC VOLUME CONTROL
Table 17 ADC Digital Volume Control
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
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:
0.5  (G-255) dB for 1  G  255;
a
w
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a
R15
Left channel
ADC Digital
Volume
R16
Right channel
ADC Digital
Volume
1
0
0
b
REGISTER
ADDRESS




1
1

2
2



1 (

f
f
tan(
tan(
b
c

/
/
a
f
f
0
s
w
w
s
)
7:0
8
7:0
8
=
b
b
=
BIT
cos(
/
/
2
2
) 2
) 2


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ADCVOLL
[7:0]
ADCVU
ADCVOLR
[7:0]
ADCVU
x (100 / 48000) = 0.01308996939 rads
x (1000 / 48000) = 0.1308996939 rads
=
0
LABEL
1
1
)


=
tan(
tan(

1 ( 
. 0
. 0
MUTE for G = 0
. 0
0130899693
0130899693
11111111
( 0dB )
Not
latched
11111111
( 0dB )
Not
latched
9869949627
DEFAULT
Left ADC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -127dB
0000 0010 = -126.5dB
… 0.5dB steps up to
1111 1111 = 0dB
ADC left and ADC right volume do not
update until a 1 is written to ADCVU (in
reg 15 or 16)
Right ADC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -127dB
0000 0010 = -126.5dB
… 0.5dB steps up to
1111 1111 = 0dB
ADC left and ADC right volume do not
update until a 1 is written to ADCVU (in
reg 15 or 16)
)
cos(
/ 9
/ 9
) 2
) 2
. 0
1308996939
= 0.9869949627
DESCRIPTION
PP, Rev 3.8, May 2012
)
=
Pre-Production
34