TDA7468D Datasheet, PDF (7/22 Pages) STMicroelectronics – TWO BANDS DIGITALLY CONTROLLED AUDIO PROCESSOR WITH BASS ALC SURROUND

TDA7468D
3 APPLICATION SUGGESTIONS
The first and the last stages are volume control blocks. The control range is 0 to -63dB (mute) with 1dB
step resolution for this first one, 0 to 24dB (mute) with 8dB step resolution for the last one.
The very high resolution allows the implementation of systems free from any noisy acoustical effect.
The TDA7468D audioprocessor provides 2 bands tones control.
3.1 Bass, Stages
The Bass cell has an internal resistor R_i = 44KΩ typical.
Several filter types can be implemented, connecting external components to the Bass IN and OUT pins.
The fig.5 refers to basic T Type Bandpass Filter starting from the filter component values (R1 internal and
R2,C1,C2 external) the centre frequency Fc, the gain Av at max. boost and the filter Q factor are computed
as follows:
F_C
=
--------------------------------¹---------------------------------
2 ⋅ π ⋅ R1 ⋅ R2 ⋅ C1 ⋅ C2
A_V = ^R-----²------^C-_R---²--₂---+--_C---^R--₁---²-+----^C-_R----¹-₂---+--_C---^R--₂---ⁱ----^C----¹-
Q = -----_RR----₂-¹----^â‹-_C---^R-₁---²--+---^â‹--_R-^C----₂-¹----_C-^â‹---^C-₂----²-
Viceversa, once F_C, A_V, and R_i internal value are fixed, the external components values will be:
C1 = -₂----_â‹---_π-----_â‹^A---_F--^V--_C--–---_â‹--¹-_R-----_i--_â‹---_Q---
C2 = -_A----_V-^Q----–-²---₁-^â‹---^C-–----^1Q-----₂-
R2 = ₂-----_â‹---_π-----_â‹---_C-----^A1----^V-_â‹---_F-–---_C-¹----_â‹-–--₍--_A-^Q---_V--²---–-----₁----₎---_â‹---_Q---
3.2 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 between treble pins and ground.
3.3 CREF
The suggested 10µF reference capacitor (CREF) value can be reduced to 4.7µF if the application requires
faster power ON.
Figure 5.
Ri internal
IN
OUT
C₁
C₂
R₂
D95AU313
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