STA308 STMicroelectronics, STA308 Datasheet - Page 29

• Manufacturer Part Number: STA308
• Description: IC AUDIO PROCESSOR DGTL 64-TQFP
• Manufacturer: STMicroelectronics
• Series: DDX™r
• Type: Audio Processorr

Specifications of STA308

• Mounting Type: Surface Mount
• Package / Case: 64-TQFP, 64-VQFP
• Case: QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Applications: -

responding to a given biquad (filter) simultaneously to avoid possible unpleasant acoustic side effects. When
using this technique, the 8-bit address would specify the address of the biquad b2 coefficient (e.g. 0, 5, 10, 15,
…, 50, … 195 decimal), and the STA308 will generate the RAM addresses as offsets from this base value to
write the complete set of coefficient data.
Equalization:
Figure 3. Data Flow for single channel Biquad / Bass / Treble block.:
Five user-programmable 28-bit biquads are available per channel in the STA308. These biquads run at 192kHz
for 48kHz, 96kHz, or 192kHz input and at 176.4kHz for 44.1kHz, 88.2kHz, and 176.4kHz input. The PreScale
block is used for attenuation when filters are to be designed that boost frequencies above 0dBFS. This is a
single 28-bit signed multiply, with 800000h = -1 and 7FFFFFh = 0.9999998808. These values are labeled
CxPS, with x representing the channel. The biquads use this equation:
Y[n] = 2(b0/2)X[n] + 2(b1/2)X[n-1] + b2X[n-2] - 2(a1/2)Y[n-1] - a2Y[n-2]
Y[n] represents the output and X[n] represents the input. Coefficients are defined in the following manner:
CxHx0 = b2
CxHx1 = b0/2
CxHx2 = -a2
CxHx3 = -a1/2
CxHx4 = b1/2
The first x represents the channel and the second the biquad number. For example C3H41 is the b0/2 coeffi-
cient in the fourth series biquad in channel 3. The biquad link bit allows all channels to use the coefficients of
channel 1.
Bass Management
Channel 6 provides the ability to scale and mix all channels before the biquad block. This allows for information
from any channel to be redirected to this channel and then filtered appropriately for a subwoofer application.
When the BME bit is set (bit D5 of Configuration Register A, at address 00h) the input to the biquad section is
routed from the scale and mix block instead of the normal channel 6 1st stage interpolation output.
Eight scaling coefficients are provided to perform this function. They are labeled CxBMS with x representing the
channel that is being scaled. Each input channel is multiplied by its corresponding scale factor and summed.
The output of the summation is the output of the scale and mix block.
= b0X[n] + b1X[n-1] + b2X[n-2] - a1Y[n-1] - a2Y[n-2]
From
1st Interpolation
Stage
PreScale
Biquad1
Biquad2
Biquad3
Biquad4
Biquad5
Treble
To
Volume/
Limiter
Bass/
STA308
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