Datasheet

2
−23
Bit
S_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx.xxxx_xxxx_xxxx_xxxx_xxxx_xxx
2
0
Bit
2
16
Bit
2
22
Bit
Sign Bit
2
23
Bit
2
−1
Bit
2
−10
Bit
M0007-02
(1 or 0) y 2
23
+ (1 or 0) y 2
22
+ … + (1 or 0) y 2
0
+ (1 or 0) y 2
−1
+ … + (1 or 0) y 2
−23
2
23
Bit 2
22
Bit 2
0
Bit 2
−1
Bit 2
−23
Bit
M0008-02
TAS5508C
SLES257–SEPTEMBER 2010 www.ti.com
concatenated with the hex value of the fractional part of the gain coefficient to form the 32-bit I
2
C
coefficient. The reason is that the 28-bit coefficient contains 5 bits of integer, and thus the integer part of
the coefficient occupies all of one hex digit and the most significant bit of the second hex digit. In the same
way, the fractional part occupies the lower three bits of the second hex digit, and then occupies the other
five hex digits (with the eighth digit being the zero-valued most significant hex digit).
2.3.2.2 48-Bit 25.23 Number Format
All level adjustment and threshold coefficients are 48-bit coefficients using a 25.23 number format.
Numbers formatted as 25.23 numbers have 25 bits to the left of the decimal point and 23 bits to the right
of the decimal point. This is shown in Figure 2-7.
Figure 2-7. 25.23 Format
Figure 2-8 shows the derivation of the decimal value of a 48-bit 25.23 format number.
Figure 2-8. Alignment of 5.23 Coefficient in 32-Bit I
2
C Word
Two 32-bit words must be sent over the I
2
C bus to download a level or threshold coefficient into the
TAS5508C. The alignment of the 48-bit, 25.23 formatted coefficient in the 8-byte (two 32-bit words) I
2
C
word is shown in Figure 2-9.
26 Description Copyright © 2010, Texas Instruments Incorporated
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