TDA7437N_06 Datasheet, PDF (27/34 Pages) STMicroelectronics – Digitally controlled audio processor

TDA7437N
Mute and pause features
5.13
Bass & mid filters
Several bass filter types can be implemented. Normally it is the basic T-type bandpass filter
that is used. Starting from the filter component values (R1 internal and R2, C1, C2 external),
the centre frequency Fc, the gain Av at max bass boost and the filter Q factor are computed
as follows:
F_c
=
--------------------------------¹----------------------------------
2 ⋅ Π ⋅ R1 ⋅ R2 ⋅ C1 ⋅ C2
A_v = ^R-----²-----^â‹---^C-_R----²-₂----+-_â‹---_CR----₁-²----+-^â‹---^C-_R----¹-₂---+-_â‹---_C-^R----₂-¹-----^â‹---^C-----¹-
5.14
Vice versa fixed Fc, Av, and R1 (internal typ.±30%), the external component values are
C1 = ---------^A-----^v----–----¹-----------
2 ⋅ Π ⋅ R1 ⋅ Q
C2 = _A-----_v^Q----–--^â‹--₁-^Q----–---^â‹--_Q-^C----¹-_â‹---_Q---
Q = ----_R-⁽--^R--₂---¹--_â‹---_C^â‹---^R-₁---²--+---^â‹--_R-^C----₂-¹----_â‹-^â‹--_C-^C---₂-²----⁾-
R2 = -₂----_â‹---_Π-------_â‹--_C-^A----^v₁----–-_â‹---_F-¹---_c-–---_â‹--^Q-₍--_A---^â‹--_v-^Q---–----₁----₎---_â‹---_Q----
Input selector
The multiplexer selector can choose one of the following inputs:
● a differential CD stereo input.
● a mono input.
● four stereo input
The signal fed to the input pins must be decoupled via series capacitors. The minimum
allowed value depends on the correspondent input impedance. For the CD diff input (Zi =
10Kohm worst case) a Cin = 4.7uF is recommended. For the other inputs (70Kohm worst
case, a Cin=1uF is recommended.
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