STA339BWS_11 Datasheet, PDF (17/76 Pages) STMicroelectronics – 2.1-channel 40-watt high-efficiency digital audio system Sound Terminal®

STA339BWS
4
Processing data paths
Processing data paths
Figure 6 and Figure 7 below show the data processing paths inside STA339BWS. The
whole processing chain is composed of two consecutive sections. In the first one,
dual-channel processing is implemented and in the second section each channel is fed into
the post-mixing block either to generate 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
cut-off frequency of the two bands).
The first section, Figure 6, begins with a 2x oversampling FIR filter providing 2 * f_S audio
processing. Then a selectable high-pass filter removes the DC level (enabled if HPB = 0).
The left and right channel processing paths can include up to 8 filters, depending on the
selected configuration (bits BQL, BQ5, BQ6, BQ7 and XO[3:0]). By default, four user
programmable, independent filters per channel are enabled, plus the preconfigured
de-emphasis, bass and treble controls (BQL = 0, BQ5 = 0, BQ6 = 0, BQ7 = 0).
If the coefficient sets for the two channels are linked (BQL = 1) it is possible to use the
de-emphasis, bass and treble filters in a user defined configuration (provided the relevant
BQx bits are set). In this case both channels use the same processing coefficients and can
have up to seven filters each. If BQL = 0 the BQx bits are ignored and the fifth, sixth and
seventh filters are configured as de-emphasis, bass and treble controls, respectively.
Figure 6. Left and right processing, section 1
Sampling
frequency=Fs
Sampling
frequency=2xFs
If BQ5=1 If BQ6=1 IF BQ7=1
and BQL=1 and BQL=1 and BQL=1
Biquad
Biquad Biquad
#5
#6
#7
x2
FxI2R
PreScale ^Hi-Pass
oFvIRer
Filter
Biquad
#1
Biquad
#2
Biquad
#3
Biquad
#4
De-Emph.
Bass
Treble
L
saomvpelring
From
I2S input
interface
If HPB=0
User Defined Filters
If DEMP=0
If C1TCB=0
BTC: Bass Boost/Cut
TTC: Treble Boost/Cut
If DSPB=0 and C1EQBP=0
If BQ5=1 If BQ6=1 IF BQ7=1
and BQL=1 and BQL=1 and BQL=1
Biquad
Biquad Biquad
#5
#6
#7
x2
FxI2R
PreScale ^Hi-Pass
oFvIRer
Filter
Biquad
#1
Biquad
#2
Biquad
#3
Biquad
#4
De-Emph.
Bass
Treble
LR
saomvpelring
If HPB=0
User Defined Filters
If DEMP=0
If C2TCB=0
BTC: Bass Boost/Cut
TTC: Treble Boost/Cut
If DSPB=0 and C2EQBP=0
Moreover, the common 8th filter can be available on both channels provided the predefined
crossover frequencies are not used, XO[3:0] = 0, and the dual-band DRC is not used.
In the second section, Figure 7, mixing and crossover filters are available. If B²DRC is not
enabled they are fully user-programmable and allow the generation of a third channel
(2.1 outputs). Alternatively, in mode B²DRC, these blocks are used to split the sub-band and
define the cut-off frequencies of the two bands. A prescaler and a final postscaler allow full
control over the signal dynamics before and after the filtering stages. A mixer function is also
available.
Doc ID 15276 Rev 5
17/76