sta333bwqs13tr STMicroelectronics, sta333bwqs13tr Datasheet - Page 57

• Manufacturer Part Number: sta333bwqs13tr
• Description: 2.1-channel High-efficiency Digital Audio System With Qsound Qhd
• Manufacturer: STMicroelectronics

STA333BWQS
6.12.19
6.12.20
6.12.21
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.
Additionally, the STA333BWQS allows specification of a high-pass filter (processing
channels 1 and 2) and a lo-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 noted 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
Pre-scale
The STA333BWQS 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 using the same I
and the bass-management. All channels can use the channel 1 pre-scale factor by setting
the Biquad link bit. By default, all pre-scale factors are set to 0x7FFFFF.
Post-scale
The STA333BWQS provides one additional multiplication after the last interpolation stage
and the distortion compensation on each channel. This post-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 using the same I
registers as the biquad coefficients and the bass-management. This post-scale 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 post-scale factor by setting the
post-scale link bit. By default, all post-scale factors are set to 0x7FFFFF. When Line output
is being utilized, channel 3 post-scale will affect both channels 3 and 4.
Over-current post-scale
The STA333BWQS provides a simple mechanism for reacting to over-current detection in
the power-block. When the ocwarn input is asserted, the over-current post-scale value is
used in place of the normal post-scale value to provide output attenuation on all channels.
The default setting provides 3 dB of output attenuation when ocwarn is asserted.
The amount of attenuation to be applied in this situation can be adjusted by modifying the
Over-current Post-scale value. As with the normal post-scale, this scaling value is a 24-bit
signed fractional multiplier, with 0x800000 = -1 and 0x7FFFFF = 0.9999998808. By default,
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
Table
69.
2
C registers as the biquad coefficients
Register description
2
C
57/71
2