TAS5504_06 datasheet(24/96 Pages) TI

24 / 96 page

Introduction

SLES123 − October 2004

TAS5504

Similarly, the TAS5504 carries additional precision in the form of overflow bits to permit the value of

intermediate calculations to exceed the input precision without clipping. The TAS5504 advanced digital audio

processor achieves both of these important performance capabilities by using a high performance digital audio

processing architecture with a 48-bit data path, 28-bit filter coefficients, and a 76-bit accumulator.

1.5

Input Crossbar Mixer

The TAS5504 has a full 8x4 input crossbar mixer. This mixer permits each signal processing channel input

to be any ratio of any of the eight input channels. The control parameters for the input crossbar mixer are

programmable via the I2C interface. See the Input Mixer Register (0x41−0x48, channels 1−8) section.

SUM

Gain Coefficient

Input 1

Gain Coefficient

Input 2

Gain Coefficient

Input 8

Figure 1−12. Input Crossbar Mixer

1.6

Biquad Filters

For 32-kHz to 96-kHz data, the TAS5504 provides 28 biquads across the four channels (seven per channel)

For 176.4-kHz and 192-kHz data, the TAS5504 has 21 biquads across the three channels (seven per

channel). All of the biquad filters are second order direct form I structure.

The direct form I structure provides a separate delay element and mixer (gain coefficient) for each node in the

biquad filter. Each mixer output is a signed 76-bit product of a signed 48-bit data sample (25.23 format number)

and a signed 28-bit coefficient (5.23 format number). The 76-bit ALU in the TAS5504 allows the 76-bit

resolution to be retained when summing the mixer outputs (filter products).

The five 28-bit coefficients for the each of the 28 biquads are programmable via the I2C interface. See

Table 1−3.

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