STA333BW_11 STMICROELECTRONICS [STMicroelectronics], STA333BW_11 Datasheet - Page 58

• Manufacturer Part Number: STA333BW_11
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Register description
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Coefficients stored in the user defined coefficient RAM are referenced in the following
manner:
where x represents the channel and the y the biquad number. For example, C2H41 is the b
coefficient in the fourth biquad for channel 2.
Crossover and biquad #8
Additionally, the STA333BW can be programmed for a high-pass filter (processing
channels 1 and 2) and a low-pass filter (processing channel 3) to be used for bass-
management crossover when the XO setting is 000 (user-defined). Both of these filters
when defined by the user (rather than using the preset crossover filters) are second order
filters that use the biquad equation given above. They are loaded into the C12H0-4 and
C3Hy0-4 areas of RAM noted in
By default, all user-defined filters are pass-through where all coefficients are set to 0, except
the b
Prescale
The STA333BW provides a multiplication for each input channel for the purpose of scaling
the input prior to EQ. This pre-EQ scaling is accomplished by using a 24-bit signed
fractional multiplier, with 0x800000 = -1 and 0x7FFFFF = 0.9999998808. The scale factor
for this multiply is loaded into RAM. All channels can use the channel-1 prescale factor by
setting the Biquad link bit. By default, all prescale factors (RAM addresses 0x32 to 0x33) are
set to 0x7FFFFF.
Postscale
The STA333BW provides one additional multiplication after the last interpolation stage and
the distortion compensation on each channel. This postscaling is accomplished by using a
24-bit signed fractional multiplier, with 0x800000 = -1 and 0x7FFFFF = 0.9999998808. The
scale factor for this multiply is loaded into RAM. This postscale factor can be used in
conjunction with an ADC equipped micro-controller to perform power-supply error
correction. All channels can use the channel-1 postscale factor by setting the postscale link
bit. By default, all postscale factors (RAM addresses 0x34 to 0x36) are set to 0x7FFFFF.
When line output is being used, channel-3 postscale affects both channels 3 and 4.
Thermal warning and overcurrent adjustment (TWOCL)
The STA333BW provides a simple mechanism for reacting to overcurrent or thermal
warning detection in the power block. When the warning occurs, the TWOCL value is used
to provide output attenuation clipping on all channels.
The amount of attenuation to be applied in this situation can be adjusted by modifying the
overcurrent and thermal warning limiting value (RAM addr 0x37). By default, the overcurrent
postscale adjustment factor is set to 0x5A9DF7 (that is, -3 dB). Once the limiting is applied,
it remains until the device is reset or according to the TWRB and OCRB settings.
CxHy0 = b
CxHy1 = b
CxHy2 = -a
CxHy3 = -a
CxHy4 = b
0
/ 2 coefficient which is set to 0x400000 (representing 0.5)
1
2
0
1
2
/ 2
/ 2
/ 2
Doc ID 13773 Rev 3
Table
71, addresses 0x28 to 0x31.
STA333BW
2