TDA7439DS Datasheet, PDF (5/16 Pages) STMicroelectronics – THREE BANDS DIGITALLY CONTROLLED AUDIO PROCESSOR

TDA7439DS
APPLICATION SUGGESTIONS
The first and the last stages are volume control
blocks. The control range is 0 to -47dB (mute) for
the first one, 0 to -79dB (mute) for the last one.
Both of them have 1dB step resolution.
The very high resolution allows the implementation
of systems free from any noisy acoustical effect.
The TDA7439DS audioprocessor provides 3
bands tones control.
Bass, Middle Stages
The Bass and the middle cells have the same
structure.
The Bass cell has an internal resistor Ri = 44KΩ
typical.
The Middle cell has an internal resistor Ri = 25KΩ
typical.
Several filter types can be implemented, connect-
ing external components to the Bass/Middle IN
and OUT pins.
Figure 1.
Ri internal
IN
OUT
C₁
C₂
R₂
D95AU313
The fig.1 refers to basic T Type Bandpass Filter
starting from the filter component values (R1 in-
ternal and R2,C1,C2 external) the centre fre-
quency Fc, the gain Av at max. boost and the fil-
ter Q factor are computed as follows:
F_C =
1
2 ⋅ π ⋅√R1⋅R2⋅C1⋅ C2
A_V
=
R2
C2 + R2 C1 + Ri
R2 C1 + R2 C2
C1
Q
=
√R1⋅ R2⋅C1⋅C2
R2 C1 + R2 C2
Viceversa, once Fc, Av, and Ri internal value are
fixed, the external components values will be:
C1
=
2
⋅
π
AV − 1
⋅ F_C ⋅ R_i
⋅
Q
C2
=
Q²
A_V −
⋅ C1
1 − Q²
R2
=
2
⋅
π
⋅
AV − 1
C1 ⋅ F_C
− Q²
⋅ (A_V −
1)
⋅Q
Treble Stage
The treble stage is a high pass filter whose time
constant is fixed by an internal resistor (25KΩ
typical) and an external capacitor connected be-
tween treble pins and ground
Typical responses are reported in Figg. 10 to 13.
CREF
The suggested 10µF reference capacitor (CREF)
value can be reduced to 4.7µF if the application
requires faster power ON.
Figure 2: THD vs. frequency
Figure 3: THD vs. R_LOAD
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