Application suggestions TDA7439
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3 Application suggestions
The first and the last stages are volume control blocks. The control range is 0 to -47 dB and
mute for the first stage and 0 to -79 dB and mute for the last one. Both control blocks have a
step resolution of 1 dB.
This very high resolution allows the implementation of systems free from any noisy
acoustical effect.
The TDA7439 audio processor provides 3 bands of tone control (bass, mid-range and
treble).
3.1 Tone control
3.1.1 Bass, mid-range stages
The bass and the mid-range cells have the same structure.
However, the bass cell has an internal resistor R
B
of typically 44 kΩ whilst the mid-range cell
has an internal resistor R
M
of typically 25 kΩ.
Several filter types can be implemented by connecting external components to the bass/mid
IN and OUT pins.
Typical responses are shown in Figure 8, Figure 9 and Figure 11.
Figure 4. Bass/mid-range filter implementation
Figure 4. refers to the basic T-type band-pass filter. Starting from the filter component values
(R1 (internal) and R2, C1, C2 (external)) then the centre frequency f
C
, the gain Av at
maximum boost and the filter Q factor are computed as follows:
Ri internal
C
2
OUTIN
C
1
R
2
D95AU313
f
C
1
2 π R1 R2 C1 C2⋅⋅⋅⋅⋅
-----------------------------------------------------------------=
A
V
R2C2 R2C1 RiC1++
R2C1 R2C2+
----------------------------------------------------------- -=
Q
R1 R2 C1 C2⋅⋅⋅
R2C1 R2C2+
-------------------------------------------------=
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