sta339bw STMicroelectronics, sta339bw Datasheet - Page 20

• Manufacturer Part Number: sta339bw
• Description: 2.1-channel High-efficiency Digital Audio System
• Manufacturer: STMicroelectronics

Processing data paths
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Processing data paths
The whole processing chain is composed of two consecutive sections. In the first one
dual-channel processing is implemented, as described below. Then each channel is fed into
the post-mixing block where there is a choice of processing, either the dual-band DRC is
disabled or it is enabled. When B
output configuration and with cross-over filters enabled, is used. When B
the 2.0 output configuration with cross-over filters for defining the cutoff frequency of the two
bands is used.
The first section,
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, four 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) then it is possible to use the de-emphasis, bass
and treble filter in a user defined configuration (provided the relevant BQx bits are set to 1).
In other words both channels 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 de-emphasis, bass and treble controls, respectively.
Moreover the common 8th filter, from the subsequent processing section, can be available
on both channels (provided the pre-defined cross-over 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 B
(lower schematic in
(2.1 outputs) to be generated. Alternatively, in B
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 dynamics before
and after, respectively, the filtering stages. A mixer function is also available.
Figure 7.
Sampling
Sampling
frequency = fs
frequency = fs
From
From
I
I
interface
interface
2
2
S input
S input
Left and right processing part 1
sampling
sampling
sampling
sampling
over
over
over
over
over
over
over
over
FIR
FIR
FIR
FIR
FIR
FIR
FIR
FIR
x2
x2
x2
x2
x2
x2
x2
x2
Figure
Figure
Sampling
Sampling
frequency = 2 * fs
frequency = 2 * fs
Pre-scale
Pre-scale
Pre-scale
Pre-scale
PreScale
PreScale
PreScale
PreScale
7, begins with a 2x oversampling FIR filter allowing a 2 * fs audio
If HPB=0
If HPB=0
If HPB=0
If HPB=0
8) they are fully user-programmable and allow a third channel
Hi-pass
Hi-pass
Hi-pass
Hi-pass
Filter
filter
Filter
filter
Filter
Filter
filter
filter
Pass
Pass
Pass
Pass
Doc ID 15251 Rev 4
2
DRC is disabled a third channel, typically used in 2.1
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
#1
#1
#1
#1
#1
#1
#1
#1
If DSPB=0 and C1EQBP=0
If DSPB=0 and C1EQBP=0
If DSPB=0 and C2EQBP=0
If DSPB=0 and C2EQBP=0
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
#2
#2
#2
#2
#2
#2
#2
#2
User-defined filters
User-defined filters
User-defined filters
User-defined filters
2
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
DRC mode (upper schematic in
#3
#3
#3
#3
#3
#3
#3
#3
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
Biquad
#4
#4
#4
#4
#4
#4
#4
#4
and BQL=1
and BQL=1
and BQL=1
and BQL=1
If DEMP=0
If DEMP=0
If DEMP=0
If DEMP=0
If BQ5=1
If BQ5=1
If BQ5=1
If BQ5=1
De-Emph.
De-Emph.
De-Emph.
De-Emph.
Biquad
Biquad
Biquad
Biquad
#5
#5
#5
#5
and BQL=1
and BQL=1
and BQL=1
and BQL=1
If C1TCB=0
If C1TCB=0
BTC: bass boost/cut
BTC: bass boost/cut
TTC: treble boost/cut
TTC: treble boost/cut
If C2TCB=0
If C2TCB=0
BTC: bass boost/cut
BTC: bass boost/cut
TTC: treble boost/cut
TTC: treble boost/cut
2
If BQ6=1
If BQ6=1
If BQ6=1
If BQ6=1
Biquad
Biquad
Biquad
Biquad
DRC is not enabled
Bass
Bass
Bass
Bass
#6
#6
#6
#6
2
DRC is enabled
and BQL=1
and BQL=1
and BQL=1
and BQL=1
IF BQ7=1
IF BQ7=1
IF BQ7=1
IF BQ7=1
Biquad
Biquad
Biquad
Biquad
Treble
Treble
Treble
Treble
#7
#7
#7
#7
STA339BW
Figure
L
L
L
L
L
L
R
R
8),