STA323W ST Microelectronics, STA323W Datasheet - Page 32

• Manufacturer Part Number: STA323W
• Description: 2.1 High Efficiency Digital Audio System
• Manufacturer: ST Microelectronics

DataSheet4U.com
www.DataSheet4U.com
DataSheet
STA323W
Table 33. Mix/Bass Management Block Diagram
After a mix is achieved, STA323W also provides the capability to implement crossver filters on all channels
corresponding to 2.1 bass management solution. Channels 1-2 use a 1st order high-pass filter and chan-
nel 3 uses a 2nd order low-pass filter corresponding to the setting of the XO bits of I2C register 0Ch. If XO
= 000, user specified crossover filters are used.
By default these coefficients correspond to pass-through. However, the user can write these coefficients
in a similar way as the EQ biquads. When user-defined setting is selected, the user can only write 2nd
order crossover filters. This output is then passed on to the Volume/Limiter block.
8.5 Calculating 24-Bit Signed Fractional Numbers from a dB Value
The pre-scale, mixing, and post-scale functions of the STA323W use 24-bit signed fractional multipliers to
attenuate signals. These attenuations can also invert the phase and therefore range in value from -1 to
+1. It is possible to calculate the coefficient to utilize for a given negative dB value (attenuation) via the
equations below.
As can be seen by the preceding equations, the value for positive phase 0dB is 0x7FFFFF and the value
for negative phase 0dB is 0x800000.
32/41
– Non-Inverting Phase Numbers 0 to +1 :
– Coefficient = Round(8388607 * 10^(dB/20))
– Inverting Phase Numbers 0 to -1 :
– Coefficient = 16777216 - Round(8388607 * 10^(dB/20))
4
U
.com
from EQ
Channel #2
from EQ
Channel #1
User-defined Mix Coefficients
C1MX1
C1MX2
C2MX1
C2MX2
C3MX1
C3MX2
+
+
+
DataSheet4U.com
Crossover Frequency determined
by XO setting.
User-defined when XO = 000
High-Pass
High-Pass
Low-Pass
Filter
Filter
Filter
XO
XO
XO
Channel#2
to GC/Vol
Channel#3
to GC/Vol
Channel#1
to GC/Vol
DataShee