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PDF MC1372 Data sheet ( Hoja de datos )
| Número de pieza | MC1372 | |
| Descripción | Color TV Video Modulator | |
| Fabricantes | Motorola Semiconductors | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MC1372 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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® MOTOROLA
MC1372
COLOR TV VIDEO MODULATOR
... an mtegrated circuit used to generate an RF TV signal from
baseband color-difference and luminance signals.
The MC1372 contains a chroma subcamer oscillator, a lead and
lag network, a quasi-quadrature suppressed carrier DSB chroma
modulator, an RF oscillator and modulator, and an LSTTL com-
patrble clock driver with adjustable duty cycle.
The MC1372 is a companion part to the MC6847 Video Display
Generator, providmg and accepting the correct de interconnection
levels. This device may also be used as a general-purpose modulator
wtth a variety of vtdeo signal generating devices such as video games,
test equipment, video tape recorders, etc.
• Single 5.0 Vdc Supply Operation for NMOS
and TTL Compatibility
• Minimal External Components
• Compatible with MC6847 Video Display Generator
• Sound Carrier Addition Capability
• Modulates Channel 3 or 4 Carrier with Encoded Vrdeo Signal
• Low Power Dissipation
• Linear Chroma Modulators for High Versatrlity
• Composrte Vrdeo Signal Generation Capability
• Ground-Referenced Video Prevents Overmodulation
COLOR TV
VIDEO
MODULATOR CIRCUIT
SILICON MONOLITHIC
INTEGRATED CIRCUIT
.~'~~ ~ ~ ~ P SUFFIX
PLASTIC PACKAGE
CASE 646-05
Pin Connections
Duty
Chromtnance
input
Lum1nance
Input
ChrorT;a
1'0odu!ator
Output
FIGURE 1- BLOCK DIAGRAM
Color 8
Input
Lum1flance
1npi..-t
RF
Modulator
Output
•
Oscillator
Input
Clock
Output
4
Grouna
Duty Cycle
Adjust
Chrorninance
1nput
e----, 41r--+-----t-D Modulator
Outpu"t
Color A
Input
Color
Reference
Input
RF Tank
3-3
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MC1372
OPERATIONAL DESCRIPTION
Pin 1 - Clock Output
Provides a rectangular ptJise output waveform with
frequency equal to the chrominance subcarrier oscillalor.
This output" capable of driving one LS-TTL load.
Pin 2- Oscillator Input
Color subcarrier oscillator feedback mput. Signal from
the clock output 's externally phase sh.fted and ac cou-
pled to this pin.
Pin 3 - Duty Cycle Adjust
A de voltage applied to this prn adjusts the duty cycle
of the clock output Signal. If the pin is left unconnected,
the duty cycle is approximately 50%
Pin 4 - Ground
Pin 5- Color B Input
De coupled mput to Chroma Modulator B, whose
phase leads modulator A by approximately 100° The
modulator output amplitude and polar:ty correspond to
the voltage difference between th1s pm and the Color
Reference Voltage at Pm 6.
Pin 6 -Color Reference Input
The de voltage appi1ed to th1s pin establishes the
reference voltage to v-..rhtch Color A and Color 8 1nputs
are compared
Pin 7 -Color A Input
De coupled tnput to Chroma Modu:ator A, whose
phase 1ags modulator B by approxrmately 100° The
modulator output a'l'lplitude and polarrty co'·respond to
the voltage d1fference between th1s pin and ~he Color
Reference Voltage at Pin 6_
Pin 8 -Chroma Modulator Output
Low impedance (emitter follower} output wh1ch
provides the vector1al sum ot chroma modulators A
and B.
Pin 9- Luminance Input
Input to R F modulator Th,s pin accepts a de coupled
luminance and sync signal. The amplitude of the R F signal
output mcreases with positive voltage appl:ed to the pm,
and ground potent•al results in zero output (:.e., 100%
modulation). A signal with positive-going sync should
be used
Pin 10- Chrominance Input
Input to the RF modulator. This pin accepts ac coupled
chrominance provided by the Chroma Modulator Output
{pin 81. The signal is reduced by an internal resistor divider
before being applied to the RF modulator. The resistor
divider consists of a 300 ohm series resistor and a 500
ohm shunt resistor. Additional garn reduction may be
obtained by the addition of external series resistance
topin10.
Pin 11- Vee
Positive supply voltage
Pin 12 - R F Modulator Output
Common collector of output modulator stage_ Output
'mpedance and stage garn may be selected by chorce of
resistor connected between this p1n and de supply.
Pins 13 and 14- RF Tank
A tuned circuit connected between these pms deter·
m·nes the RF oscillator frequency. The tuned c1rcwt must
prov)de a low de resistance shunt. Applymg a de offset
voltage between these pms results m baseband comoos1te
vrdeo at the RF Modulator Output.
MC1372 CIRCUIT DESCRIPTION
The chrommance oscillator and clo-ck dnver cons~st ot
em1tter follower 04 and mverting ampl.fier 05. S1gnal
presented at clock dnver output pin 1 ;s coupled to
oscillator mput P·'1 2 through a:-1 external RC and crys"tal
network, which provides 180° phase sh, ft at the resonant
frequency. The dutv cycle of the output waveform <S
determined by the de component at oin 1 lflternally
coupled through R 12 to the base of 04_ As prn 1 de
voltage increases, a smaller port;on ot the smuso1dai
feedback srgnal at prn 2 exceeds the 04 base vortage of
two Lmes VsE reqt.;ired for conduct1on. As the de level
s reduced. device 04 and thus 05 rs turned on for a
longer percentage of the cycle. Trans.stors 00, 01,
02 and d10de 01 provide the biasing network whtch
determmes the de operating level of the osc,l!ator. The
tranSistor 02 and resiStors R5, R6, and R 7 form a voltage
refe•ence of four times VBE at the collector of 02. The
clc voltage at p;n 1 1s determ ned by the va.ues of R4,
RS, and R 12 and the applred du:y cycle adjust voltage
at pm 3. Smce these resistors ate nominally equal. the
voltage at pin 1 w·ll always approximate the de voltage
at pin 3.
The oscillator s1gnal at ptn 1 is Internally coupled to
active filter 044. This filter reduces the frequency content
above 4 MHz. The output of the Liter at the emitter of
044 is ac coupled through C3 to the i:-1put of the lead/lag
network. R32 and Cl provrde approximately 50° of phase
lag, whde C2 and R29 provrde approximately 50° of
phase lead. These two quasi-quadrature waveforms are
used to switch chroma modulators B and A, respectively.
The transistors 022 through 025 and 032-033 form
a doubly balanced modulator. The rnput signal applied
at pin 5 IS compared to the color de reference voltage
applied at pin 6 in differentral amplrfier 032-033. The
source current provided by transistor 034 1S partit1oned
in transistors 032 and 033 according to the differential
rnput signal. The bases of transistors 023 and 024 are
connected to the de reference voltage at the emrtter of
030. The bases of transistors 022 and 025 are connected
•
3-7
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| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MC1372.PDF ] | |
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