STA350B datasheet(76/94 Pages) STMICROELECTRONICS

76 / 94 page

STA350B, STA350BW

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DocID018572 Rev 7

8.18

Extended configuration register (addr 0x36)

The extended configuration register provides access to B2DRC and biquad 5, 6 and 7.

8.18.1

Dual-band DRC

The STA350Bx device provides a dual-band DRC (B2DRC) on the left and right channels

data path, as depicted in Figure 32. Dual-band DRC is activated by setting MDRC[1:0] = 1x.

Figure 32. B2DRC scheme

The low frequency information (LFE) is extracted from left and right channels, removing the

high frequencies using a programmable biquad filter, and then computing the difference with

the original signal. Limiter 1 (DRC1) is then used to control left/right high-frequency

amplitude of the components, while limiter 2 (DRC2) is used to control the low-frequency

components (see Chapter 8.11).

The cutoff frequency of the high-pass filters can be user-defined, XO[3:0] = 0, or selected

from the pre-defined values.

DRC1 and DRC2 are then used to independently limit L/R high frequencies and LFE

channels amplitude (see Chapter 8.11) as well as their volume control. To be noted that, in

this configuration, the dedicated channel 3 volume control can actually act as a bass boost

enhancer as well (0.5 dB/step resolution).

The processed LFE channel is then recombined with the L and R channels in order to

reconstruct the 2.0 output signal.

Sub-band decomposition

The sub-band decomposition for B2DRC can be configured specifying the cutoff frequency.

The cutoff frequency can be programmed in two ways, using XO bits in register 0x0C, or

using the “user programmable” mode (coefficients stored in RAM addresses 0x28 to 0x31).

Mdrc[1]

Mdrc[0]

PS48DB

XAR1

XAR2

BQ5

BQ6

BQ7

0000

Pass

Filter

Pass

Filter

B2DRC

Hi-pass

filter

B2DRC

Hi-pass

filter

CH1

Volume

Vol

And

Limiter

DRC1

CH2

Volume

DRC1

CH3

Volume

Vol

And

Limiter

DRC2

CH3

Volume

Vol

And

Limiter

DRC2

Pass

Filter

Pass

Filter

B2DRC

Hi-pass

filter

B2DRC

Hi-pass

filter

CH1

Volume

Vol

And

Limiter

DRC1

CH2

Volume

DRC1

CH3

Volume

Vol

And

Limiter

DRC2

CH3

Volume

Vol

And

Limiter

DRC2

AM045194v1

STA350B Datasheet(PDF) 76 Page - STMicroelectronics

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