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PDF LM1889 Data sheet ( Hoja de datos )
| Número de pieza | LM1889 | |
| Descripción | LM1889 TV Video Modulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM1889 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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PRELIMINARY
April 1987
LM1889 TV Video Modulator
General Description
The LM1889 is designed to interface audio color difference
and luminance signals to the antenna terminals of a TV re-
ceiver It consists of a sound subcarrier oscillator chroma
subcarrier oscillator quadrature chroma modulators and
RF oscillators and modulators for two low-VHF channels
The LM1889 allows video information from VTR’s games
test equipment or similar sources to be displayed on black
and white or color TV receivers When used with the
MM57100 and MM53104 a complete TV game is formed
Features
Y dc channel switching
Y 12V to 18V supply operation
Y Excellent oscillator stability
Y Low intermodulation products
Y 5 Vp-p chroma reference signal
Y May be used to encode composite video
Block Diagram
DC Test Circuit
Dual-In-Line Package
Order Number LM1889N
See NS Package Number N18A
TL H 7917 – 1
C1995 National Semiconductor Corporation TL H 7917
TL H 7917 – 2
RRD-B30M115 Printed in U S A
1 page  
Typical Performance Characteristics
Sound Carrier Oscillator
Supply Dependence
(fo e 4 5 MHz)
RF Oscillator Frequency
Supply Dependence
(fo e 67 25 MHz)
Chroma Modulator
Transconductance Bandwidth
IOUT 13 V1 or 18
Chroma Modulator
Common-Mode Input Range
Pins 2 3 4
RF Modulator
Common-Mode Input Range
Pins 12 13 (Application Circuit)
Circuit Description (Refer to Circuit Diagram)
The sound carrier oscillator is formed by differential amplifi-
er Q3 Q4 operated with positive feedback from the pin 15
tank to the base of Q4
The chroma oscillator consists of the inverting amplifier
Q16 Q17 and Darlington emitter follower Q11 Q12 An ex-
ternal RC and crystal network from pin 17 to pin 18 provides
an additional 180 degrees phase lag back to the base of
Q17 to produce oscillation at the crystal resonance frequen-
cy (See AC test circuit)
The feedback signal from the crystal is split in a lead-lag
network to pins 1 and 18 respectively to generate the sub-
carrier reference signals for the chroma modulators The R-
Y modulator consists of multiplier devices Q29 Q30 and
Q21 – Q24 while the B-Y modulator consists of Q31 Q32
and Q25 –Q28 The multiplier outputs are coupled through a
balanced summing amplifier Q37 Q38 to the input of the RF
modulators at pin 13 With 0 offset at the lower pairs of the
multipliers no chroma output is produced However when
either pin 2 or pin 4 is offset relative to pin 3 a subcarrier
output current of the appropriate phase is produced at pin
13
TL H 7917 – 4
The channel B oscillator consists of devices Q56 and Q57
cross-coupled through level-shift zener diodes Q54 and
Q55 A current regulator consisting of devices Q39 – Q43 is
used to achieve good RF frequency stability over supply and
temperature The channel B modulator consists of multiplier
devices Q58 Q59 and Q50 – Q53 The top quad is coupled
to the channel B tank through isolating devices Q48 and
Q49 A dc offset between pins 12 and 13 offsets the lower
pair to produce an output RF carrier at pin 10 That carrier is
then modulated by both the chroma signal at pin 13 and the
video and sound carrier signals at pin 12 The channel A
modulator shares pin 12 and 13 buffers Q45 and Q44 with
channel B and operates in an identical manner
The current flowing through channel B oscillator diodes
Q54 Q55 is turned around in Q60 Q61 and Q62 to source
current for the channel B RF modulator In the same man-
ner the channel A oscillator Q71 – Q74 uses turn around
Q77 Q78 and Q79 to source the channel A modulator One
oscillator at a time may be activated by connecting its tank
to supply (see ac test circuit) The corresponding modulator
is then activated by its current turn-around and the other
oscillator modulator combination remains ‘‘OFF’’
5
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| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LM1889.PDF ] | |
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