TAS5717_14 Datasheet, PDF (31/68 Pages) Texas Instruments – 10-W/15-W Digital Audio Power Amplifier with Integrated Cap-Free HP Amplifier

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TAS5717
TAS5719
SLOS655A – NOVEMBER 2010 – REVISED FEBRUARY 2011
PWM LEVEL METER
The structure in Figure 42 shows the PWM level meter that can be used to study the power profile.
Post-DAP Processing
Ch1
ABS
a
1–a
Z^–1
32-Bit Level
rms
ADDR = 0x6B
Ch2
ABS
a
1–a
I²C Registers
(PWM Level Meter)
Z^–1
rms
32-Bit Level
ADDR = 0x6C
Figure 42. PWM Level Meter Structure
B0396-01
26-Bit 3.23 Number Format
All mixer gain coefficients are 26-bit coefficients using a 3.23 number format. Numbers formatted as 3.23
numbers means that there are 3 bits to the left of the binary point and 23 bits to the right of the binary point. This
is shown in Figure 43 .
2^–23 Bit
2^–5 Bit
2^–1 Bit
2⁰ Bit
2¹ Bit
Sign Bit
S_xx.xxxx_xxxx_xxxx_xxxx_xxxx_xxx
M0125-01
Figure 43. 3.23 Format
The decimal value of a 3.23 format number can be found by following the weighting shown in Figure 43. 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 44 applied to obtain the magnitude
of the negative number.
2¹ Bit
2⁰ Bit
2^–1 Bit
2^–4 Bit
2^–23 Bit
(1 or 0) ´ 2¹ + (1 or 0) ´ 2⁰ + (1 or 0) ´ 2^–1 + ....... (1 or 0) ´ 2^–4 + ....... (1 or 0) ´ 2^–23
M0126-01
Figure 44. Conversion Weighting Factors—3.23 Format to Floating Point
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