Datasheet

B0155-01
LB1
RB2
Atten
LB2
L
+
+
+
+
+
–
–
+
+
R
ToLeftChannel
ToRightChannel
TLV320AIC3007
SLOS619 – APRIL 2009 ..................................................................................................................................................................................................... www.ti.com
The coefficients for this filter implement a variety of sound effects, with bass-boost or treble boost being the most
commonly used in portable audio applications. The default N and D coefficients in the part are given in Table 3
and implement a shelving filter with 0 dB gain from DC to approximately 150 Hz, at which point it rolls off to a 3
dB attenuation for higher frequency signals, thus giving a 3 dB boost to signals below 150 Hz. The N and D
coefficients are represented by 16-bit two ’ s complement numbers with values ranging from – 32768 to 32767.
Table 3. Default Digital Effects Processing Filter Coefficients,
When in Independent Channel Processing Configuration
Coefficients
N0 = N3 D1 = D4 N1 = N4 D2 = D5 N2 = N5
27619 32131 – 27034 – 31506 26461
The digital processing also includes capability to implement 3-D processing algorithms by providing means to
process the mono mix of the stereo input, and then combine this with the individual channel signals for stereo
output playback. The architecture of this processing mode, and the programmable filters available for use in the
system, is shown in Figure 27 . Note that the programmable attenuation block provides a method of adjusting the
level of 3-D effect introduced into the final stereo output. This combined with the fully programmable biquad filters
in the system enables the user to fully optimize the audio effects for a particular system and provide extensive
differentiation from other systems using the same device.
Figure 27. Architecture of the Digital Audio Processing When 3-D Effects are Enabled
It is recommended that the digital effects filters should be disabled while the filter coefficients are being modified.
While new coefficients are being written to the device over the control port, it is possible that a filter using
partially updated coefficients may actually implement an unstable system and lead to oscillation or objectionable
audio output. By disabling the filters, changing the coefficients, and then re-enabling the filters, these types of
effects can be entirely avoided.
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