wm9081 Wolfson Microelectronics plc, wm9081 Datasheet - Page 63

• Manufacturer Part Number: wm9081
• Description: Mono Dac With 2.6w Class Ab/d Speaker Driver, Dynamic Range Controller And Retune Mobile Parametric Equalizer
• Manufacturer: Wolfson Microelectronics plc

Pre-Production
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The companded data is also inverted as recommended by the G.711 standard (all 8 bits are inverted
for μ-law, all even data bits are inverted for A-law). The data will be transmitted as the first 8 MSBs
of data.
Companding converts 13 bits (μ-law) or 12 bits (A-law) to 8 bits using non-linear quantization. This
provides greater precision for low amplitude signals than for high amplitude signals, resulting in a
greater usable dynamic range than 8 bit linear quantization. The companded signal is an 8-bit word
comprising sign (1 bit), exponent (3 bits) and mantissa (4 bits).
8-bit mode is selected whenever DAC_COMP=1. The use of 8-bit data allows samples to be passed
using as few as 8 BCLK cycles per LRCLK frame. When using DSP mode B, 8-bit data words may
be transferred consecutively every 8 BCLK cycles.
8-bit mode (without Companding) may be enabled by setting DAC_COMPMODE=1 when
DAC_COMP=0.
Table 36 8-bit Companded Word Composition
Figure 51 μ-Law Companding
120
100
80
60
40
20
0
F(x) = A|x| / ( 1 + lnA)
F(x) = ( 1 + lnA|x|) / (1 + lnA)
SIGN
BIT7
0
0.1
0.2
0.3
EXPONENT
BIT[6:4]
u-law Companding
0.4
Normalised Input
0.5
for x ≤ 1/A
for 1/A ≤ x ≤ 1
0.6
MANTISSA
0.7
BIT[3:-0]
0.8
0.9
PP, Rev 3.0, April 2009
1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
WM9081
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