WM8948 Datasheet, PDF (75/189 Pages) Wolfson Microelectronics plc – Stereo Low-Power CODEC with Video Buffer and Touch Panel Controller

Production Data
WM8948
REGISTER
ADDRESS
R5 (05h)
Companding
control
BIT
LABEL
3
DAC_COMP
2
DAC_COMP
MODE
1
ADC_COMP
0
ADC_COMP
MODE
Table 46 Companding Control
DEFAULT
DESCRIPTION
0
DAC Companding Enable
0 = Disabled
1 = Enabled
0
DAC Companding Mode
0 = μ-law
1 = A-law
0
ADC Companding Enable
0 = Disabled
1 = Enabled
0
ADC Companding Mode
0 = μ-law
1 = A-law
Companding uses a piecewise linear approximation of the following equations (as set out by ITU-T
G.711 standard) for data compression:
μ-law (where μ=255 for the U.S. and Japan):
F(x) = ln( 1 + μ|x|) / ln( 1 + μ)
} for -1 ≤ x ≤ 1
A-law (where A=87.6 for Europe):
F(x) = A|x| / ( 1 + lnA)
} for x ≤ 1/A
F(x) = ( 1 + lnA|x|) / (1 + lnA)
} for 1/A ≤ x ≤ 1
120
100
80
60
40
20
0
0
u-law Companding
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Normalised Input
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
Figure 29 μ-Law Companding
w
PD, May 2011, Rev 4.1
75