TAS5518 Datasheet, PDF (26/102 Pages) Texas Instruments – TAS5518 8 Channel Digital Audio PWM Processor

Introduction
uuuu
uuuu
uuuu
Sign
Bit
Integer
Digit 4
(Bits 2³ − 2¹)
Integer
Digit 1
Integer
Digit 2
Integer
Digit 3
uuuu
Sxxx
xxxx
xxxx
xxxx
Word 1
(Most
Significant
Word)
Coefficient
Digit 16
Coefficient
Digit 15
Coefficient
Digit 14
Coefficient
Digit 13
Coefficient
Digit 12
Coefficient
Digit 11
Coefficient
Digit 10
Coefficient
Digit 9
Integer
Digit 4
(Bit 2⁰)
Fraction
Digit 6
Integer
Integer
Fraction
Fraction
Fraction
Fraction
Fraction
Digit 5
Digit 6
Digit 1
Digit 2
Digit 3
Digit 4
Digit 5
0
xxxx
xxxx
x. x x x
xxxx
xxxx
xxxx
xxxx
xxxx
Word 2
(Least
Significant
Word)
Coefficient
Digit 8
Coefficient
Digit 7
Coefficient
Digit 6
Coefficient
Digit 5
Coefficient
Digit 4
Coefficient
Digit 3
Coefficient
Digit 2
Coefficient
Digit 1
u = unused or don’t care bits
Digit = hexadecimal digit
Figure 1−12. Alignment of 25.23 Coefficient in Two 32-Bit I²C Words
1.5.2.3 TAS5518 Audio Processing
The TAS5518 digital audio processing is designed such that noise produced by filter operations is maintained
below the smallest signal amplitude of interest, as shown in Figure 1−13. The TAS5518 achieves this by
increasing the precision of the signal representation substantially above the number of bits that are absolutely
necessary to represent the input signal.
Ideal Input
Possible Outputs
Desired Output
Maximum Signal
Amplitude
Overflow
Values retained by
overflow bits
Signal bits
input
Filter
Operation
Reduced
SNR signal
output
Signal bits
output
Noise Floor with no
additional precision
Noise Floor as a
result of additional
precision
Figure 1−13. TAS5518 Digital Audio Processing
SLES115 — August 2004
TAS5518
17