TDA7403 Datasheet, PDF (8/26 Pages) STMicroelectronics – BASIC SIGNAL PROCESSOR

TDA7403
Figure 4. Loudness @ Attn. = 15dB, fc = 400Hz
(dB)
D98AU844
-5
Figure 5. Softmute Timing
1
EXT.
MUTE
-10
-15
-20
10
100
1,000
Hz
Softmute
The digitally controlled softmute stage allows
muting/demuting the signal with a I²C bus pro-
grammable slope. The mute process can either
be activated by the softmute pin or by the I²C
bus. The slope is realized in a special S shaped
curve to mute slow in the critical regions (see fig-
ure 5).
For timing purposes the Bit 3 of the I²C bus out-
put register is set to 1 from the start of muting un-
til the end of demuting.
+SIGNAL
REF
-SIGNAL
1
I²C BUS
OUT
D97AU634
Time
Note: Please notice that a started Mute action is always terminated
and could not be interrupted by a change of the mute signal.
Figure 6. Soft Step Timing
VOUT
2dB
1dB
Softstep Volume
When volume level is changed often an audible
click appears at the output. The root cause of
those clicks could be either a DC offset before
the volume stage or the sudden change of the
envelope of the audio signal. With the Softstep
feature both kinds of clicks could be reduced to a
minimum and are no more audible (see figure 6).
Bass
There are three parameters programmable in the
bass stage (see figs 7, 8, 9, 10):
- Attenuation
- Center Frequency (60, 70, 80 and 100Hz)
- Quality Factors (1, 1.25, 1.5 and 2)
DC Mode
In this mode the DC gain is increased by 4.4dB.
In addition the programmed center frequency and
quality factor is decreased by 25% which can be
used to reach alternative center frequencies or
quality factors.
-1dB
-2dB
10ms
Time
D97AU635
Note: For steps more than 1dB the softstep mode should be
deactivated because it could generate a 1dB error during the
blend-time
Treble
There are two parameters programmable in the
treble stage (see figs 11, 12):
- Attenuation
- Center Frequency (10, 12.5, 15 and 17.5kHz).
Speaker Attenuator
Due to practical aspects the steps in the speaker
attenuators are not linear over the full range. At
attenuations more than 24dB the steps increase
from 1.5dB to 10dB (please see data byte specifi-
cation).
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