sta339bws STMicroelectronics, sta339bws Datasheet - Page 66

• Manufacturer Part Number: sta339bws
• Description: 2.1-channel High-efficiency Digital Audio System
• Manufacturer: STMicroelectronics

Register description
6.18.1
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Dual-band DRC
STA339BWS device provide a dual-band DRC (B
path, as depiceted in
Figure 20. B
The low frequency information (LFE) are 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
components amplitude while limiter 2 (DRC2) is used to control the low frequencies
components (see
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
this configuration, the dedicatedchannel 3 volume control can be actually acted 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 B
The cut off frequency can be programmed in two ways, using XO bits in register 0x0C, or
using “user programmable” mode (coefficients stored in RAM adresses 0x28 to 0x31).
For the user programmable mode, use the formulae below to compute the high pass filters:
where alpha = (1-sin(ω
R
R
R
R
L
L
L
L
b0 = (1 + alpha) / 2
b1 = -(1 + alpha) / 2
b2 = 0
2
DRC scheme
Chapter
Figure
0
))/cos(ω
Chapter
6.11).
20. Dual-band DRC is activated by setting MDRC[1:0] = 1x.
Hi-pass
Hi-pass
Hi-pass
Hi-pass
Pass
Pass
B
B
Pass
Pass
B
B
0
Filter
Filter
Filter
Filter
2
2
filter
filter
2
2
filter
filter
DRC
DRC
DRC
DRC
), and ω
6.11) as well as their volume control. To be noted that, in
2
XO
XO
XO
XO
DRC can be configured specifying the cutoff frequency.
0
a0 = 1
a1 = -alpha
a2 = 0
is the cutoff frequency.
-
-
-
-
2
DRC) on the left and right channels data
Volume
Volume
Volume
Volume
Volume
Volume
Volume
Volume
Ch1
Ch1
Ch3
Ch3
Ch3
Ch3
Ch2
Ch2
DRC1
DRC1
DRC2
DRC2
DRC2
DRC2
DRC1
DRC1
Limiter
Limiter
Limiter
Limiter
Limiter
Limiter
And
And
And
And
And
And
Vol
Vol
Vol
Vol
Vol
Vol
STA339BWS
+
+
+
+