TAS5705
www.ti.com ...................................................................................................................................................................................................... SLOS549–JUNE 2008
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 I2C interface.
The following steps are invovled in using a loudness biquad with the volume comprensation feature:
1. Program the biquad with a loudness filter.
2. Program 0x26 (1/G) and 0x28 (scale).
3. Enable volume compensation in register 0x0E.
b0
x(n)
y(n)
Magnitude
Truncation
S
b1
a1
z–1
z–1
b2
a2
z–1
z–1
M0012-02
Figure 47. Biquad Filter
Subchannel Preprocessing
A subchannel has three input multiplexers that can select from the bass management output, the downmix
output, or the channel-6 input multiplexer output.
Register 0x21, bits (9:8) determine the submultiplexer selection, defined in Table 4.
Table 4. Submultiplexer Selection
Bits
00
Submultiplexer
Pass through channel-6 input multiplexer output
01
Select bass management block output for submultiplexer
Select downmix ouput for submultiplexer
10
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