Datasheet

Noise Floor With No
Additional Precision
Maximum Signal Amplitude
Ideal Input Possible Outputs Desired Output
Filter
Operation
Signal
Bits
Input
Overflow
Reduced
SNR
Signal
Output
Noise Floor as a Result
of Additional Precision
Signal
Bits
Output
Values Retained by
Overflow Bits
M0010-01
TAS5548
SLES270 –NOVEMBER 2012 www.ti.com
As Figure 3-9 shows, the hexadecimal (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 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).
3.2.3 TAS5548 Audio Processing
The TAS5548 digital audio processing is designed so that noise produced by filter operations is
maintained below the smallest signal amplitude of interest, as shown in Figure 3-10. The device achieves
this low noise level by increasing the precision of the signal representation substantially above the number
of bits that are absolutely necessary to represent the input signal.
Similarly, the TAS5548 carries additional precision in the form of overflow bits to permit the value of
intermediate calculations to exceed the input precision without clipping. The TAS5548's advanced digital
audio processor achieves both of these important performance capabilities by using a high-performance
digital audio-processing architecture with a 32-bit data path, 28-bit filter coefficients, and a 60-bit
accumulator.
Figure 3-10. TAS5548 Digital Audio Processing
3.3 Input Crossbar Mixer
The TAS5548 has a full 10×8 input crossbar mixer. This mixer permits each signal-processing channel
input to be any mix of any of the eight input channels, as shown in Figure 3-11. The control parameters for
the input crossbar mixer are programmable via the I
2
C interface. See the Input Mixer Registers, Channels
1–8 (0x41–0x48), Section 11.20, for more information.
20 TAS5548 DAP Architecture Copyright © 2012, Texas Instruments Incorporated
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