wm8988 Wolfson Microelectronics plc, wm8988 Datasheet - Page 27

• Manufacturer Part Number: wm8988
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

Production Data
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GRAPHIC EQUALISER
The WM8988 has a digital graphic equaliser and adaptive bass boost function. This function
operates on digital audio data before it is passed to the audio DACs. Bass enhancement can take
two different forms:
•
•
Treble control applies a user programmable gain, without any adaptive boost function. Bass and
treble control are completely independent with separately programmable gains and filter
characteristics.
Table 18 Graphic Equaliser
R12 (0Ch)
Bass Control
R13 (0Dh)
Treble Control
REGISTER
ADDRESS
Linear bass control: bass signals are amplified or attenuated by a user programmable
gain. This is independent of signal volume, and very high bass gains on loud signals
may lead to signal clipping.
Adaptive bass boost: The bass volume is amplified by a variable gain. When the bass
volume is low, it is boosted more than when the bass volume is high. This method is
recommended because it prevents clipping, and usually sounds more pleasant to the
human ear.
7
6
3:0
6
3:0
BIT
BB
BC
BASS
[3:0]
TC
TRBL
[3:0]
LABEL
0
0
1111
(Disabled)
0
1111
(Disabled)
DEFAULT
Bass Boost
0 = Linear bass control
1 = Adaptive bass boost
Bass Filter Characteristic
0 = Low Cutoff (130Hz at 48kHz sampling)
1 = High Cutoff (200Hz at 48kHz sampling)
Bass Intensity
Code
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Treble Filter Characteristic
0 = High Cutoff (8kHz at 48kHz sampling)
1 = Low Cutoff (4kHz at 48kHz sampling)
Treble Intensity
0000 or 0001 = +9dB
0010 = +7.5dB
… (1.5dB steps)
1011 to 1110 = -6dB
1111 = Disable
DESCRIPTION
BB=0
+9dB
+9dB
+7.5dB
+6dB
+4.5dB
+3dB
+1.5dB
0dB
-1.5dB
-3dB
-4.5dB
-6dB
-6dB
-6dB
-6dB
Bypass (OFF)
PD, Rev 4.0, October 2008
BB=1
15 (max)
14
13
12
11
10
9
8
7
6
5
4
3
2
1
WM8988
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