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TDA7418TR

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TDA7418 Description of the audioprocessor
13/29
selected and an undesired mute would appear at the outputs. For such applications, it can
be switched in the AutoZero-Remain-Mode (Bit 6 of the subaddress-byte). If this bit is set to
high, the AutoZero will not be invoked and the old adjustment-value remains.
4.3 Loudness
There are four parameters programmable in the loudness stage:
4.3.1 Attenuation
Figure 4 shows the attenuation as a function of frequency at f
C
= 400Hz
Figure 4. Loudness attenuation @ f
C
= 400Hz.
4.3.2 Peak frequency
Figure 5 shows the four possible peak-frequencies at 400, 800 and 2400Hz
Figure 5. Loudness center frequencies @ Attn. = 15dB
Description of the audioprocessor TDA7418
14/29
4.3.3 Low and high frequency boost
Figure 6 shows the different Loudness shapes in low & high frequency boost.
Figure 6. Loudness attenuation, fc = 2.4kHz
4.3.4 Flat mode
In flat mode the loudness stage works as a 0dB to -15dB attenuator.
4.4 SoftMute
The digitally controlled SoftMute stage allows muting/demuting the signal with a I
2
C-bus
programmable slope. The mute process can either be activated by the SoftMute pin or by
the I
2
C-bus. This slope is realized in a special S-shaped curve to mute slow in the critical
regions (see Figure 7).
For timing purposes the Bit0 of the I
2
C-bus output register is set to 1 from the start of muting
until the end of demuting.
Figure 7. Softmute timing
1. Please notice that a started Mute-action is always terminated and could not be interrupted by a change of
the mute-signal
1
EXT.
MUTE
+SIGNAL
REF
-SIGNAL
1
I
2
C BUS
OUT
Time
D97AU634
TDA7418 Description of the audioprocessor
15/29
4.5 SoftStep volume
When the volume-level is changed audible clicks could appear at the output. The root cause
of those clicks
could either be 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.
Eight programmable softstep time from one step to the next are user selectable.
Figure 8. SoftStep timing
1. For steps more than 1dB the SoftStep mode should be deactivated because it could generate 1dB error
step during the blend-time.
4.6 Bass
There are four parameters programmable in the bass stage:
4.6.1 Attenuation
Figure 9 shows the attenuation as a function of frequency at a center frequency of 80Hz.
Figure 9. Bass control @ f
C
= 80Hz, Q = 1
1dB
0.5dB
-0.5dB
-1dB
Time
D00AU1170
V
OUT
SS Time
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TDA7418TR

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Manufacturer:
STMicroelectronics
Description:
Audio DSPs 3 Band Car Audio Processor 8-10V
Lifecycle:
New from this manufacturer.
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