TDA7404DTR Datasheet, PDF (21/35 Pages) STMicroelectronics – Car radio signal processor

TDA7404
Description of functionality
4.9
External AC - coupling
TDA7404 has external AC coupling terminals which can be selected one of two positions
behind the mixing stage or bass filter.
Figure 16. External AC coupling
Input
AC O U T
SW1
a
b
M ixin g
S t a ge
SW3
SOUND
EFFECTS
Volu m e & F ilt er
AC I N
SW2
a
b
ACC select or
SW4
Speaker
The external AC coupling is selected in position of four switches controlled by the lower 2bit
in the Others selection (seeTable 6).
Table 6. Others selection
D1
D0
Switch position
X
0 SW3 = ON, SW4 = ON (selected internal pass), SW1 = b, SW2 = open
0
1 SW3 = OFF, SW4 = ON, SW1 = a, SW2 = a
1
1 SW3 = ON, SW4 = OFF, SW1 = b, SW2 = b
4.10
Speaker attenuator
Due to practical aspects the steps in the speaker-attenuator are not linear over the full
range. At attenuations more than 24 dB the steps increase from 1.5 dB to 10 dB (please see
data byte specification).
4.11
Subwoofer attenuator
The Subwoofer output is a single ended stereo output. The attenuator is exactly the same
like the other speakers.
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