TAS5508C datasheet(29/107 Pages) TI

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TAS5508C

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SLES257 – SEPTEMBER 2010

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), as shown in Figure 2-12. The 76-bit ALU in

the TAS5508C 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 56 biquads are programmable via the I2C interface. See

Table 2-3.

Figure 2-12. Biquad Filter Structure

All five coefficients for one biquad filter structure are written to one I2C register containing 20 bytes (or five

32-bit words). The structure is the same for all biquads in the TAS5508C. Registers 0x51–0x88 show all

the biquads in the TAS5508C. Note that u[31:28] bits are unused and default to 0x0.

Table 2-3. Contents of One 20-Byte Biquad Filter Register (Default = All-Pass)

INITIALIZATION GAIN COEFFICIENT VALUE

DESCRIPTION

DECIMAL

HEX

b0 coefficient

u[31:28], b0[27:24], b0[23:16], b0[15:8], b0[7:0]

1.0

0x00, 0x80, 0x00, 0x00

b1 coefficient

u[31:28], b1[27:24], b1[23:16], b1[15:8], b1[7:0]

0.0

0x00, 0x00, 0x00, 0x00

b2 coefficient

u[31:28], b2[27:24], b2[23:16], b2[15:8], b2[7:0]

0.0

0x00, 0x00, 0x00, 0x00

a1 coefficient

u[31:28], a1[27:24], a1[23:16], a1[15:8], a1[7:0]

0.0

0x00, 0x00, 0x00, 0x00

a2 coefficient

u[31:28], a2[27:24], a2[23:16], a2[15:8], a2[7:0]

0.0

0x00, 0x00, 0x00, 0x00

2.6

Bass and Treble Controls

From 32-kHz to 96-kHz data, the TAS5508C has four bass and treble tone controls. Each control has a

±18-dB control range with selectable corner frequencies and second-order slopes. These controls operate

four channel groups:

•

L, R, and C (channels 1, 2, and 7)

•

LS, RS (channels 3 and 4)

•

LBS, RBS (alternatively called L and R lineout) (channels 5 and 6)

•

Sub (channel 8)

For 176.4-kHz and 192-kHz data, the TAS5508C has two bass and treble tone controls. Each control has

a ±18-dB I2C control range with selectable corner frequencies and second-order slopes. These controls

operate two channel groups:

Description

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