TDA7439 Datasheet, PDF (6/19 Pages) STMicroelectronics – THREE BANDS DIGITALLY CONTROLLED AUDIO PROCESSOR

TDA7439
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----^R1----²-+---^C--_R---¹--₂---+-_C----^R-₂----ⁱ-^C-----¹--
Q = -----^R-_R----¹-₂---^â‹_C---^R--₁---²--+---^â‹--_R-^C----₂-¹---_C--^â‹--₂-^C----²--
Viceversa, once Fc, Av, and Ri 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-–---¹-_Q-----₂-
R2 = -₂----_â‹---_π-----_â‹---_C-----^A1----^V-_â‹---_F^–----_c-¹---_â‹--–-₍---_AQ----_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 Typical responses are reported in Figg.
10 to 13.
3.3 CREF
The suggested 10µF reference capacitor (CREF) value can be reduced to 4.7µF if the application requires
faster power ON.
Figure 6. THD vs. frequency
Figure 7. THD vs. RLOAD
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