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| 型號： | TDA7460ND |
| 廠商： | STMICROELECTRONICS |
| 元件分類： | 消費家電 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO20 |
| 封裝： | ROHS COMPLIANT, SOP-20 |
| 文件頁數(shù)： | 25/49頁 |
| 文件大?。?/td> | 473K |
| 代理商： | TDA7460ND |
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TDA7460ND
Stereo decoder part
5.6.1
Trigger path
The incoming MPX signal is highpass filtered, amplified and rectified. This second order
highpass-filter has a corner frequency of 140kHz. The rectified signal, RECT, is lowpass
filtered to generate a signal called PEAK. Also noise with a frequency 140 kHz increases the
PEAK voltage. The PEAK voltage is fed to a threshold generator, which adds to the PEAK
voltage a DC dependent threshold VTH. Both signals, RECT and PEAK+VTH are fed to a
comparator which triggers a re-triggerable monoflop. The monoflop's output activates the
sample-and-hold circuits in the signal path for 40
μs.
The block diagram of the noise blanker is given in Figure 26.
Figure 26.
Block diagram of the noise blanker
5.6.2
Automatic noise controlled threshold adjustment (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 noise blanker byte)
b)
the noise adjusted threshold in 4 steps (bits D3 and D4 of the noise blanker byte,
see Figure 17.).
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 operation is high.
If the MPX signal is noisy the PEAK voltage increases 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 Figure 17.).
5.6.3
Automatic threshold control
Besides the noise controlled threshold adjustment there is an additional possibility for
influencing the trigger threshold. It is depending on the stereo blend control.
The point where the MPX signal starts to become noisy is fixed by the RF part. Therefore
also the starting point of the normal noise-controlled trigger adjustment is fixed (fig. 16). In
some cases the behavior of the noise blanker can be improved by increasing the threshold
even in a region of higher fieldstrength. Sometimes a wrong triggering occurs for the MPX
signal often shows distortion in this range which can be avoided even if using a low
threshold.
Because of the overlap of this range and the range of the stereo/mono transition it can be
controlled by stereo blend. This threshold increase is programmable in 3 steps or switched
off with bits D0 and D1 of the fieldstrength control byte.
+
-
RECTIFIER
LOWPASS
RECT
+
THRESHOLD
GENERATOR
VTH
PEAK
ADDITIONAL
THRESHOLD
CONTROL
MONOFLOP
HOLDN
MPX
D98AU861
HIGH PASS
相關(guān)PDF資料 |
PDF描述 |
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| TDA7460NDTR | SPECIALTY CONSUMER CIRCUIT, PDSO20 |
| TDA7461ND | SPECIALTY CONSUMER CIRCUIT, PDSO28 |
| TDA7461NDTR | SPECIALTY CONSUMER CIRCUIT, PDSO28 |
| TDA7461N | SPECIALTY CONSUMER CIRCUIT, PDIP28 |
| TDA7462D | SPECIALTY CONSUMER CIRCUIT, PDSO28 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TDA7460NDTR | 功能描述:音頻 DSP CARRADIO SIGNAL PROCESSOR RoHS:否 制造商:Texas Instruments 工作電源電壓: 電源電流: 工作溫度范圍: 安裝風(fēng)格: 封裝 / 箱體: 封裝:Tube |
| TDA7461 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:CAR RADIO SIGNAL PROCESSOR |
| TDA7461D | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:CAR RADIO SIGNAL PROCESSOR |
| TDA7461N | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:CAR RADIO SIGNAL PROCESSOR |
| TDA7461N_03 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:CAR RADIO SIGNAL PROCESSOR |
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