Datasheet

Loudness Function
Volume
Biquad(0x24)
From
Input
Mux
To
Output
Mux
Loudness
Biquad(0x23)
Gain=G
1ifVol 1/G
0ifVol 1/G+1/Scale
1 Scale(Vol 1/G)otherwise
£
³
- -
0ifVol 1/G
1ifVol 1/G+1/Scale
Scale(Vol 1/G)otherwise
£
³
-
B0273-01
Scale=1/(1 1/G)-
TAS5716
www.ti.com ............................................................................................................................................................................................... SLOS569 – JANUARY 2009
The TAS5716 provides a direct form-I biquad for loudness on the subwoofer channel. The first biquad is
contained in a gain-compensation circuit that maintains the overall system gain at 1 or less to prevent clipping at
loud volume settings. This gain compensation is shown in Figure 46
Figure 46. Biquad Gain-Control Structure
Table 1. Loudness Table Example for Gain = 4, 1/G = 0.25, Scale = 1.33
Volume 0.125 0.25 0.375 0.5 0.625 0.75 0.875 1 1.125 1.25 1.375 1.5 1.625 1.75 1.875 2
Biquad path 1 1 0.833 0.666 0.5 0.333 0.166 0 0 0 0 0 0 0 0 0
Direct path 0 0 0.166 0.333 0.5 0.666 0.833 1 1 1 1 1 1 1 1 1
Total gain 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
The biquads are implemented in a direct form-I architecture. The direct form-I structure provides a separate delay
element and mixer (gain coefficient) for each node in the biquad filter.
The five 26-bit (3.23) coefficients for the biquad are programmable via the I
2
C interface.
The following steps are involved in using a loudness biquad with the volume compensation feature:
1. Program the biquad with a loudness filter.
2. Program 0x26 (1/G) and 0x28 (scale).
3. Enable volume compensation in register 0x0E.
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Product Folder Link(s): TAS5716