STA381BW datasheet(29/171 Pages) STMICROELECTRONICS

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STA381BW

Device overview

Doc ID 018835 Rev 7

29/171

4.3.1

STC block diagram

Figure 8.

STCompressorTM block diagram

The STC takes as input 2 channels and every channel is processed independently (i.e. an

independent DRC for each band of each channel) following the steps listed below

(Figure 8):

Splits the input signal into 2 bands (band splitter)

Measures the level of the signal (level meter)

Computes the attenuation (mapper)

Applies the attenuation and offset (attenuator)

The band splitter settings are common to both the processing channels while the settings of

the remaining blocks can be independently set for each band of each processing channel.

Caution:

All the settings explained hereafter apply only to the behavior of the STCompressorTM. For

the settings concerning other device operating configurations (see Chapter 4.1: Processing

data path) please refer to the appropriate paragraphs and registers.

4.3.2

Band splitter

The band splitter block is used to divide the signal into 2 sub-bands (typically low- and high-

frequency bands). This is done through two 2nd order biquads (IIR filters) for each band,

thus allowing to have up to a 4th order filter per band. This feature guarantees a totally flat

band recombination (see Figure 9). Using different filtering orders, indeed, causes a non-

negligible gain around the filter’s cutoff frequency, endangering the overall audio fidelity and,

eventually, also the safety of the speaker. The sub-band recombination can be enabled or

disabled.

Level

Meter

Mapper

Atten uato r

Offs et

Level

Meter

Mapper

Atten uato r

Offs et

Band

Sp litter

Band 0

(Lo w freqs)

Band 1

(Hig h freqs)

In p ut

Ch 0

O utp ut

Ch 0

DRC 0

DRC 1

Lev el

Meter

Mapper

Atten uato r

Offset

Lev el

Meter

Mapper

Atten uato r

Offset

Band

Sp litter

Band 0

(Lo w freqs )

Band 1

(Hig h freqs)

In p ut

Ch 1

O utp ut

Ch 1

DRC 2

DRC 3

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