TDA7400DTR STMicroelectronics, TDA7400DTR Datasheet - Page 16

• Manufacturer Part Number: TDA7400DTR
• Description: IC PROCESSOR CAR SIGNAL 28SOIC
• Manufacturer: STMicroelectronics
• Type: Car Signal Processorr

Specifications of TDA7400DTR

• Applications: Automotive Audio
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 497-3977-2

TDA7400D
Figure 13. Signals During Stereodecoder’s
off adjustment which is able to compensate the
lowpass behaviour of the tuner section. If the
tuner attenuation at 38kHz is in a range from
13.8% to 24.6% the TDA7400D needs no exter-
nal network in front of the MPX pin. Within this
range an adjustment to obtain at least 40dB
channel separation is possible.
The bits for this adjustment are located together
with the fieldstrength adjustment in one byte. This
gives the possibility to perform an optimization
step during the production of the carradio where
the channel separation and the fieldstrength con-
trol are trimmed.
The setup of the Stereoblend characteristics
which is programmable in a wide range is de-
scribed in 2.8.
Deemphasis and Highcut.
The lowpass filter for the deemphasis allows to
choose between a time constant of 50 s and
75 s (bit D
The highcut control range will be in both cases
(between VHCH and VHCL) the LEVEL signal
is converted into a 5 bit word which controls the
lowpass
5 bits independently of the absolute voltage
range between the VHCH and VHCL values.
The highcut function can be switched off by I
bus (bit D
The setup of the highcut characteristics is de-
scribed in 2.9.
PLL and Pilot Tone Detector
The PLL has the task to lock on the 19kHz pilo-
16/28
HC
Deemp
SOFTMUTE
= 2
COMMAND
STD MUTE
. There by the resolution will remain always
V
7
, Fieldstrength byte set to "0").
time
O
Deemp
7
Softmute
, Stereodecoder byte).
. Inside the highcut control range
constant
between
D97AU638
Deemp
t
t
t
...3
2
C
thresholds are available. The detector output (sig-
nal STEREO, see block diagram) can be checked
by reading the status byte of the TDA7400D via
I
Figure 14. Internal Stereoblend Characteristics
tone during a stereo transmission to allow a cor-
rect demodulation. The included detector enables
the demodulation if the pilot tone reaches the se-
lected pilot tone threshold V
Fieldstrength Control
The fieldstrength input is used to control the high
cut and the stereoblend function. In addition the
signal can be also used to control the noise-
blanker thresholds and as input for the multipath
detector. These additional functions are de-
scribed in sections 3.3 and 4.
LEVEL Input and Gain
To suppress undesired high frequency modula-
tion on the highcut and stereoblend function the
LEVEL signal is lowpass filtered firstly.
The filter is a combination of a 1st order RC low-
pass at 53kHz (working as anti-aliasing filter) and
a 1st-order switched capacitor lowpass at 2.2kHz.
The second stage is a programmable gain stage
to adapt the LEVEL signal internally to different IF
device (see Testmode section 5 LEVELINTERN).
The gain is widely programmable in 16 steps
from 0dB to 10dB (step = 0.67dB). These 4 bits
are located together with the Roll-Off bits in the
"Stereodecoder Adjustment" byte to simplify a
possible adaptation during the production of the
carradio.
Stereoblend Control
The stereoblend control block converts the inter-
2
C bus.
PTHST
. Two different