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参数资料
| 型号： | TDA7400 |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 消费家电 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PQFP44 |
| 封装： | 10 X 10 MM, TQFP-44 |
| 文件页数： | 8/28页 |
| 文件大小： | 274K |
| 代理商： | TDA7400 |
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adjustment which is able to compensate the low-
pass behaviour of the tuner section. If the tuner
attenuation at 38kHz is in a range from 13.8% to
24.6% the TDA7400 needs no external network
in front of the MPX pin. Within this range an ad-
justment to obtain at least 40dB channel separa-
tion 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 D7, Stereodecoder byte).
The highcut control range will be in both cases
τHC = 2 τDeemp. Inside the highcut control range
(between VHCH and VHCL) the LEVEL signal
is converted into a 5 bit word which controls the
lowpass
time
constant
between
τDeemp...3
τDeemp. There by the resolution will remain always
5 bits independently of the absolute voltage
range between the VHCH and VHCL values.
The highcut function can be switched off by I
2C
bus (bit D7, Fieldstrength byte set to "0").
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-
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 VPTHST. Two different
thresholds are available. The detector output (sig-
nal STEREO, see block diagram) can be checked
by reading the status byte of the TDA7400 via I
2C
bus.
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-
SOFTMUTE
COMMAND
STD MUTE
VO
t
D97AU638
t
Figure 13. Signals During Stereodecoder’s
Softmute
Figure 14. Internal Stereoblend Characteristics
TDA7400
16/28
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| TDA7400D | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:ADVANCED CAR SIGNAL PROCESSOR |
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| TDA7401 | 功能描述:音频 DSP Digital Audio Proc RoHS:否 制造商:Texas Instruments 工作电源电压: 电源电流: 工作温度范围: 安装风格: 封装 / 箱体: 封装:Tube |
| TDA7401013TR | 功能描述:音频 DSP Digital Audio Proc RoHS:否 制造商:Texas Instruments 工作电源电压: 电源电流: 工作温度范围: 安装风格: 封装 / 箱体: 封装:Tube |
| TDA7401D | 功能描述:音频 DSP Digital Audio Proc RoHS:否 制造商:Texas Instruments 工作电源电压: 电源电流: 工作温度范围: 安装风格: 封装 / 箱体: 封装:Tube |
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