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参数资料
| 型号： | TDA7403D |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 消费家电 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO20 |
| 封装： | SO-20 |
| 文件页数： | 7/25页 |
| 文件大小： | 232K |
| 代理商： | TDA7403D |
Highcut Control
The highcut control setup is similar to the
stereoblend control setup : the starting point
VHCH can be set with 2 bits to be 42, 50, 58 or
66% of REF5V whereas the range can be set to
be 17 or 33% of VHCH (see fig. 17).
FUNCTIONAL DESCRIPTION OF THE NOISE-
BLANKER
In the automotive environment the MPX signal is
disturbed by spikes produced by the ignition and
for example the wiper motor. The aim of the
noiseblanker part is to cancel the audible influ-
ence of the spikes. Therefore the output of the
stereodecoder is held at the actual voltage for
40
s.
In a first stage the spikes must be detected but to
avoid a wrong triggering on high frequency
(white) noise a complex trigger control is imple-
mented. Behind the triggerstage a pulse former
generates the "blanking" pulse. To avoid any
crosstalk to the signalpath the noiseblanker is
supplied by his own biasing circuit.
Trigger Path
The incoming MPX signal is highpass filtered,
amplified and rectified. This second order high-
pass-filter has a corner frequency of 140kHz. The
rectified signal, RECT, is lowpass filtered to gen-
erate a signal called PEAK. Also noise with a fre-
quency 140kHz increases the PEAK voltage. The
PEAK voltage is fed to a threshold generator,
which adds to the PEAK voltage a DC depend-
ent threshold VTH. Both signals, RECT and
PEAK+VTH are fed to a comparator which trig-
gers a re-triggerable monoflop. The monoflop’s
output activates the sample-and-hold circuits in
the signalpath for 40
s.
The block diagram of the noiseblanker is given in
fig.18.
Automatic Noise Controlled Threshold Adjust-
ment (ATC)
There are mainly two independent possibilities for
programming the trigger threshold:
a the low threshold in 8 steps (bits D0 to D2 of
the noiseblanker byte)
b the noise adjusted threshold in 4 steps
(bits D3 and D4 of the noiseblanker byte,
see fig. 13).
The low threshold is active in combination with a
good MPX signal without any noise; the PEAK
voltage is less than 1V. The sensitivity in this op-
eration is high.
If the MPX signal is noisy the PEAK voltage in-
creases due to the higher noise, which is also
rectified. With increasing of the PEAK voltage the
trigger threshold increases, too.
This particular
gain is programmable in 4 steps (see fig. 10).
LOWPASS
TIME CONSTANT
D97AU640
τDeemp
FIELDSTRENGHT
VHCH
VHCL
3
τDeemp
Figure 17. Highcut characteristics
+
-
RECTIFIER
LOWPASS
RECT
+
THRESHOLD
GENERATOR
VTH
PEAK
ADDITIONAL
THRESHOLD
CONTROL
MONOFLOP
HOLDN
MPX
D98AU861
HIGH PASS
Figure 18. Block diagram of the noiseblanker
TDA7403
15/25
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相关代理商/技术参数 |
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|---|---|
| TDA7403DTR | 功能描述:音频 DSP Basic Signal Process 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 |
| TDA7404 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:CARRADIO-SIGNAL-PROCESSOR |
| TDA7404_08 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Car radio signal processor |
| TDA7404D | 功能描述:音频 DSP Car Radio Signal 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 |
| TDA7404DTR | 功能描述:音频 DSP Car Radio Signal 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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