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參數(shù)資料
| 型號： | TDA8722 |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | IIC-bus programmable modulator for negative video modulation and FM sound(負(fù)向視頻調(diào)制和調(diào)頻聲的IIC總線可編程調(diào)制器) |
| 中文描述： | IIC總線可編程調(diào)制器調(diào)制負(fù)視頻和FM聲音（負(fù)向視頻調(diào)制和調(diào)頻聲的進(jìn)口證總線可編程調(diào)制器） |
| 文件頁數(shù)： | 19/28頁 |
| 文件大?。?/td> | 196K |
| 代理商： | TDA8722 |
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1998 Jun 23
19
Philips Semiconductors
Product specification
I
2
C-bus programmable modulator for
negative video modulation and FM sound
TDA8722
Fig.11 Typical picture-to-sound ratio as a function
of the value of C17.
R17 = 120 k
.
(1) 4.5 MHz.
(2) 5.5 MHz.
(3) 6.0 MHz.
(4) 6.5 MHz.
handbook, halfpage
0
10
20
40
20
16
12
MBE399
30
C17 (pF)
P/S
(dB)
(1)
(2)
(4)
(3)
Fig.12 Typical level of RF harmonics for an
asymmetrical application.
handbook, halfpage
harmonics
(dBc)
450
550
18
26
30
22
MBE400
650
750
850
RF (MHz)
third harmonic
second harmonic
VHF operation
This IC can operate on frequencies as low as 200 MHz
(and especially for VHF 3 band) provided the impedance
of the tuned circuit between pins 4 and 6 is >1 k
.
NICAM and stereo
Because of the fact that the ADJUST pin (pin 17) is an
access point to the RF mixer, it is possible to use this pin
to inject an external modulated subcarrier into the IC.
This is especially interesting when it is necessary to
transmit a second frequency modulated audio subcarrier
for stereo sound (f = 5.72 MHz) or a NICAM QPSK
modulated carrier for digital audio transmission
(f = 5.85 or 6.552 MHz).
The incoming signal must be externally modulated either
in FM with the desired signal corresponding to PAL B/G
specification for stereo sound transmission, or in QPSK in
accordance with the NICAM transmission system.
The input impedance on pin 17 is approximately 3500
,
the incoming signal must be capacitive coupled, the
resistor R17 between pin 17 and ground must remain to
adjust the modulation depth, the capacitor C17 between
pin 17 and ground may be changed depending on the
capacitance brought on by the incoming network. If this
capacitance is large, it is possible to remove C17.
Figure 13 shows a possible application for injecting such
kind of signal into the modulator IC.
Following this application, to get a picture-to-second
sound carrier ratio of
20 dB, it is necessary to apply a
level of approximately 800 mV (peak-to-peak value) at
the second carrier input, when the picture-to-first sound
carrier ratio is approximately
13 dB.
In addition, the internal FM sound modulator can be
switched off by short-circuiting pins 2 and 3.
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相關(guān)代理商/技術(shù)參數(shù) |
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| TDA8722M | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:I2C-bus programmable modulator for negative video modulation and FM sound |
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| TDA8730 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:PLL FM demodulator for DBS signals |
| TDA8732 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:NICAM-728 demodulator NIDEM |
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