Datasheet

u
Coefficient
Digit 8
u
u u S x x x
Coefficient
Digit 7
x.
x x x
Coefficient
Digit 6
x
x x x
Coefficient
Digit 5
x
x x x
Coefficient
Digit 4
x
x x x
Coefficient
Digit 3
x
x x x
Coefficient
Digit 2
x
x x x
Coefficient
Digit 1
Fraction
Digit 5
Sign
Bit
0
Fraction
Digit 6
Fraction
Digit 4
Fraction
Digit 3
Fraction
Digit 2
Fraction
Digit 1
Integer
Digit 1
u = unused or don’t care bits
Digit = hexadecimal digit
M0009-01
(1 or 0) y 2
3
+ (1 or 0) y 2
2
+ … + (1 or 0) y 2
0
+ (1 or 0) y 2
−1
+ … + (1 or 0) y 2
−4
+ … + (1 or 0) y 2
−23
2
3
Bit 2
2
Bit 2
0
Bit 2
−1
Bit 2
−4
Bit 2
−23
Bit
M0008-01
2
−23
Bit
S_xxxx.xxxx_xxxx_xxxx_xxxx_xxxx_xxx
2
−4
Bit
2
−1
Bit
2
0
Bit
Sign Bit
2
3
Bit
M0007-01
TAS5548
www.ti.com SLES270 –NOVEMBER 2012
3.2.2 28-Bit 5.23 Number Format
All mixer gain coefficients are 28-bit coefficients using a 5.23 number format. Numbers formatted as 5.23
numbers have 5 bits to the left of the binary point and 23 bits to the right of the binary point. This is shown
in Figure 3-7.
Figure 3-7. 5.23 Format
The decimal value of a 5.23 format number can be found by following the weighting shown in Figure 3-8. If
the most significant bit is logic 0, the number is a positive number, and the weighting shown yields the
correct number. If the most significant bit is a logic 1, then the number is a negative number. In this case,
every bit must be inverted, a 1 added to the result, and then the weighting shown in Figure 3-8 applied to
obtain the magnitude of the negative number.
Figure 3-8. Conversion Weighting Factors—5.23 Format to Floating Point
Gain coefficients, entered via the I
2
C bus, must be entered as 32-bit binary numbers. The format of the
32-bit number (4-byte or 8-digit hexadecimal number) is shown in Figure 3-9.
Figure 3-9. Alignment of 5.23 Coefficient in 32-Bit I
2
C Word
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