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E-TDA7400DTR

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For timing purposes the Bit 3 of the I
2
C bus out-
put register is set to 1 from the start of muting un-
til the end of demuting.
Bass
There are four parameters programmable in the
bass stage: (see figs 6, 7, 8, 9):
Attenuation
Figure 6 shows the attenuation as a function of
frequency at a center frequency at a center fre-
quency of 80Hz.
Central Frequency
Figure 7 shows the four possible center frequen-
cies 60,70,80 and 100Hz.
Quality Factors
Figure 8 shows the four possible quality factors 1,
1.25, 1.5 and 2.
DC Mode
In this mode the DC gain is increased by 5.1dB.
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.
TREBLE
There are two parameters programmable in the
treble stage (see figs 10, 11):
Attenuation
Figure 10 shows the attenuation as a function of
frequency at a center frequency of 17.5KHz.
Center Frequency
Figure 11 shows the four possible Center Fre-
quency (10, 12.5, 15 and 17.5kHz).
Speaker Attenuator
The speaker attenuators have exactely the same
structure and range like the Volume stage.
1
EXT.
MUTE
+SIGNAL
REF
-SIGNAL
1
I
2
C BUS
OUT
Time
D97AU634
Figure 5. Softmute Timing
0.0
2.5
5.0
7.5
10.0
12.5
15.0
10.0 100.0 1.0K 10.0K
Figure 7. Bass Center @ Gain = 14dB, Q = 1
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
10.0 100.0 1.0K 10.0K
Figure 6. Bass Control @ fc = 80Hz, Q = 1
Note: Please notice that a started Mute action is always terminated
and could not be interrupted by a change of the mute signal.
TDA7400D
13/28
Obsolete Product(s) - Obsolete Product(s)
0.0
2.5
5.0
7.5
10.0
12.5
15.0
10.0 100.0 1.0K 10.0K
Figure 9. Bass normal and DC Mode @ Gain =
14dB, fc = 80Hz
Note: In general the center frequency, Q and DC-mode can be set
independently. The exception from this rule is the mode (5/xx1111xx)
where the center frequency is set to 150Hz instead of 100Hz.
0. 0
2. 5
5. 0
7. 5
10. 0
12. 5
15. 0
10. 0 100.0 1. 0K 10.0K
Figure 8. Bass Quality factors @ Gain = 14dB,
fc = 80Hz
0.0
2.5
5.0
7.5
10.0
12.5
15.0
10.0 100.0 1.0K 10.0K
Figure 11. Treble Center Frequencies
@ Gain = 14dB
- 15.0
- 10.0
-5.0
0. 0
5. 0
10. 0
15. 0
10. 0 100. 0 1. 0K 10. 0K
Figure 10. Treble Control @ fc = 17.5KHz
TDA7400D
14/28
Obsolete Product(s) - Obsolete Product(s)
FUNCTIONAL DESCRIPTION OF STEREODE-
CODER
The stereodecoder part of the TDA7400D (see
Fig. 12) contains all functions necessary to de-
modulate the MPX signal like pilot tone depend-
ent MONO/STEREO switching as well as
"stereoblend" and "highcut" functions.
Stereodecoder Mute
The TDA7400D has a fast and easy to control
RDS mute function which is a combination of the
audioprocessor’s softmute and the high-ohmic
mute of the stereodecoder. If the stereodecoder
is selected and a softmute command is sent (or
activated through the SM pin) the stereodecoder
will be set automatically to the high-ohmic mute
condition after the audio signal has been soft-
muted.
Hence a checking of alternate frequencies could
be performed. To release the system from the
mute condition simply the unmute command must
be sent: the stereodecoder is unmuted immedi-
ately and the audioprocessor is softly unmuted.
Fig. 13 shows the output signal V
O
as well as the
internal stereodecoder mute signal. This influ-
ence of Softmute on the stereodecoder mute can
be switched off by setting bit 3 of the Softmute
byte to "0". A stereodecoder mute command (bit
0, stereodecoder byte set to "1") will set the
stereodecoder in any case independently to the
high-ohmic mute state.
If any other source than the stereodecoder is se-
lected the decoder remains muted and the MPX
pin is connected to Vref to avoid any discharge of
the coupling capacitor through leakage currents.
Ingain + Infilter
The Ingain stage allows to adjust the MPX signal
to a magnitude of about 1Vrms internally which is
the recommended value. The 4th order input filter
has a corner frequency of 80KHz and is used to
attenuate spikes and nose and acts as an anti al-
lasing filter for the following switch capacitor fil-
ters.
Demodulator
In the demodulator block the left and the right
channel are separated from the MPX signal. In
this stage also the 19 kHz pilot tone is cancelled.
For reaching a high channel separation the
TDA7400D offers an I2C bus programmable roll-
INGAIN
3.5 ... 11dB
STEP 2.5dB
INFILTER
LP 80KHz
4.th ORDER
DEMODULATOR
- PLOT CANC
- ROLL-OFF COMP.
- LP 25KHz
PLL +
PILOT-DET.
F19
NOISE BLANKER
F38
STEREO
HOLDN
SB CONTROL
DEEMPHASIS
+ HIGHCUT
t=50 or 75µs
REF 5V
VSBL
MPINFL
LEVEL INTERN
HC
CONTROL
VHCCH
VHCCL
-
MULTIPATH
DETECTOR
D
A
MP_OUT
LEVEL INPUT
LP 2.2KHZ
1.th ORDER
MP_IN
LEVEL
FM_L
FM_R
MPX
100K
D98AU855
GAIN 0..10dB
MPLEVELOUT
QUALITY DETECTOR
QUAL
NOISE
+
Figure 12. Block Diagram of the Stereodecoder
TDA7400D
15/28
Obsolete Product(s) - Obsolete Product(s)
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E-TDA7400DTR

Mfr. #:
Buy E-TDA7400DTR
Manufacturer:
STMicroelectronics
Description:
IC PROCESSOR CAR SIGNAL 28SOIC
Lifecycle:
New from this manufacturer.
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