STA326 STMicroelectronics, STA326 Datasheet - Page 44

• Manufacturer Part Number: STA326
• Description: DIG AUDIO SYSTEM, 2-CH, 36POWERSSOP
• Manufacturer: STMicroelectronics

Specifications of STA326

• Svhc: No SVHC (15-Dec-2010)
• No. Of Pins: 36
• Operating Temperature Range: -20°C To +85°C
• Supply Voltage Max: 36V
• Supply Voltage Min: 10V
• Termination T: RoHS Compliant
• Package / Case: PowerSO
• Interface: I2C
• Interface Type: I2C
• Rohs Compliant: Yes

User programmable processing
7
7.1
7.2
7.3
44/57
User programmable processing
EQ - biquad equation
The biquads use the equation that follows. This is diagrammed in
where Y[n] represents the output and X[n] represents the input. Multipliers are 28-bit signed
fractional multipliers, with coefficient values in the range of 0x800000 (-1) to 0x7FFFFF
(0.9999998808).
Coefficients stored in the user defined coefficient RAM are referenced in the following
manner:
The x represents the channel and the y the biquad number. For example C3H41 is the b0/2
coefficient in the fourth biquad for channel 3
Figure 17. Biquad filter
Prescale
The prescale block which precedes the first biquad is used for attenuation when filters are
designed that boost frequencies above 0 dBFS. This is a single 28-bit signed multiplier, with
0x800000 = -1 and 0x7FFFFF = 0.9999998808. By default, all prescale factors are set to
0x7FFFFF.
Postscale
The STA326 provides one additional multiplication after the last interpolation stage and
before the distortion compensation on each channel. This is a 24-bit signed fractional
multiplier. The scale factor for this multiplier is loaded into RAM using the same I
as the biquad coefficients and the mix. All channels can use the same settings as channel 1
by setting the postscale link bit.
CxHy0 = b1/2
CxHy1 = b2
CxHy2 = -a1/2
CxHy3 = -a2
CxHy4 = b0/2
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]
Z
Z
-1
-1
= b0X[n] + b1X[n - 1] + b2X[n - 2] - a1Y[n - 1] - a2Y[n - 2]
b
b
0
1
/2
/2
b
2
Doc ID 11531 Rev 3
2
2
+
+
+
2
-a
2
-a
1
/2
Figure 17
Z
Z
-1
-1
below.
2
C registers
STA326