TAS3103DBT datasheet(62/146 Pages) TI

62 / 146 page

3−2

Gain coefficients, entered via the I2C 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 3−3.

Coefficient

Digit 8

Coefficient

Digit 7

Coefficient

Digit 6

Coefficient

Digit 5

Coefficient

Digit 4

Coefficient

Digit 3

Coefficient

Digit 2

Coefficient

Digit 1

Fraction

Digit 5

Sign

Bit

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

Figure 3−3. Alignment of 5.23 Coefficient in 32-Bit I2C Word

As Figure 3−3 shows, the hex value of the integer part of the gain coefficient cannot be concatenated with the hex

value of the fractional part of the gain coefficient to form the 32-bit I2C 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 3 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).

3.1.2

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 means that there are 25 bits to the left of the decimal point and 23 bits to the right of the

decimal point. This is shown in Figure 3−4.

2−23 Bit

S_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx.xxxx_xxxx_xxxx_xxxx_xxxx_xxx

20 Bit

216 Bit

222 Bit

Sign Bit

223 Bit

2−1 Bit

2−10 Bit

Figure 3−4. 25.23 Format

TAS3103DBT Datasheet(PDF) 62 Page - Texas Instruments

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