STA369BW datasheet(25/88 Pages) STMICROELECTRONICS

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STA369BW

Processing data paths

Doc ID 022033 Rev 1

25/88

Processing data paths

Figure 16 and 17 illustrate the data processing paths inside the STA369BW.

The whole processing chain is composed of two consecutive sections. In the first one, dual-

channel processing is implemented, as described below, and then each channel is fed into

the post-mixing block allowing to generate either a third channel (typically used in 2.1 output

configuration and with crossover filters enabled) or to have the channels processed by the

dual-band DRC block (2.0 output configuration with crossover filters used to define the cutoff

frequency of the two bands).

The first section begins with a 2x oversampling FIR filter allowing for 2*Fs audio processing.

Then a selectable high-pass filter removes the DC level (enabled if HFB=0).

The channel 1 and 2 processing chain can include up to 8 filters, depending on the selected

configuration (bits BQL, BQ5, BQ6, BQ7 and XO[3:0]).

By default 4 independent filters per channel are enabled, plus the pre-configured De-

Emphasis, Bass and Treble controls (BQL=0, BQ5=0, BQ6=0, BQ7=0).

If the coefficient sets are linked (BQL=1) it’s then possible to use De-Emphasis, Bass and

Treble filters in a user-defined configuration (provided the relevant BQx bits are set). In other

words, both channels will use the same processing coefficients and can have up to 7 filters

each. Note that if BQL=0 the BQx bits are ignored and the 5th, 6th and 7th filters are

configured as, respectively, De-Emphasis, Bass and Treble controls.

Moreover the common 8th filter, from the subsequent processing section, can be available

on both channels (provided the pre-defined crossover frequencies are not used, XO[3:0]=0,

and the dual-band DRC is not used).

In the second section mixing and crossover filters are available. If B2DRC is not enabled

(Figure 17), they are fully user-programmable and allow generating a third channel (2.1

outputs). Alternatively, in B2DRC mode, those blocks will be used to split the sub-band and

define the cutoff frequencies of the two bands. A prescaler and a final post-scaler allow full

control over the signal dynamic respectively before and after the filtering stages. A mixer

function is also available.

Figure 16.

Left and right processing - part 1

From

I2S input

interface

PreScale

Hi-Pass

Filter

Biquad

If HPB=0

User Defined Filters

If DSPB=0 and C1EQBP=0

FIR

over

Sampling

frequency=Fs

Sampling

frequency=2xFs

From

I2S input

interface

PreScale

Hi-Pass

Filter

Biquad

De-Emph.

If DEMP=0

FIR

over

sampling

Sampling

frequency=Fs

Sampling

frequency=2xFs

Bass

Treble

If C1TCB=0

BTC: Bass Boost/Cut

TTC: Treble Boost/Cut

PreScale

Hi-Pass

Filter

Biquad

If HPB=0

User Defined Filters

If DSPB=0 and C2EQBP=0

FIR

over

PreScale

Hi-Pass

Filter

Biquad

De-Emph.

If DEMP=0

FIR

over

sampling

Bass

Treble

If C2TCB=0

BTC: Bass Boost/Cut

TTC: Treble Boost/Cut

If BQ5=1

and BQL=1

Biquad

If BQ6=1

and BQL=1

Biquad

IF BQ7=1

and BQL=1

Biquad

If BQ5=1

and BQL=1

Biquad

If BQ6=1

and BQL=1

Biquad

IF BQ7=1

and BQL=1

Biquad

AM045181v1

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