LM1291N

Manufacturer Part NumberLM1291N
DescriptionVideo PLL System for Continuous Sync Monitors
ManufacturerNational Semiconductor
LM1291N datasheet
 


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LM1291
Video PLL System for Continuous-Sync Monitors
General Description
The LM1291 is an integrated horizontal time base solution
specifically designed to operate in continuous-sync video
monitors It automatically synchronizes to any H frequency
from 22 kHz to 125 kHz and provides the drive pulse to the
high power deflection circuit
Available sync processing includes a vertical sync separator
and a composite video sync stripper An internal sync selec-
tion scheme gives highest priority to separate H and V sync
then composite sync and finally sync on video no external
switching between sync sources is necessary The LM1291
provides polarity-normalized H HV and V sync outputs
along with logic flags which show the respective input polar-
ities
The design uses an on-chip FVC (Frequency-to-Voltage
Converter) to set the center frequency of the VCO (Voltage-
Controlled Oscillator) This technique allows autosync oper-
ation over the entire frequency range using just one opti-
mized set of external components
The system includes a second phase detector which com-
pensates for storage time variation in the horizontal output
transistor the picture’s horizontal position is thus indepen-
dent of temperature and component variance
The LM1291 provides DC control pins for H Drive duty cycle
and flyback phase
Connection Diagram
C 1995 National Semiconductor Corporation
TL H 12323
Features
Wide continuous autosync range 22 kHz to 125 kHz
Y
(1 5 7) with no component switching or external adjust-
ments
No manufacturing trims required internal VCO capaci-
Y
tor trimmed on chip
No costly high-precision components needed
Y
Low phase jitter (1 3 ns at 100 kHz)
Y
DC controlled H phase and duty cycle
Y
Video mute pulse for blanking during H frequency
Y
transitions
Input sync prioritization
Y
Clamp pulse position and width control
Y
Continuous clamp pulse output even with no sync input
Y
Resistor-programmable minimum and maximum VCO
Y
frequency
X-ray input disables H drive and mutes video until V
Y
powered down
H drive disabled for V
Y
CC k
Horizontal output transistor protected against accidental
Y
turn-on during flyback
Capacitor-programmable frequency ramping df
Y
protects H output transistor during scanning mode
changes
FIGURE 1
Order Number LM1291N
See NS Package Number N28B
June 1995
CC
9 5V
dt
VCO
TL H 12323– 1
RRD-B30M115 Printed in U S A

LM1291N Summary of contents