LM1291 Datasheet, PDF (1/12 Pages) National Semiconductor (TI) – Video PLL System for Continuous-Sync Monitors

June 1995
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
Features
Y _{Wide continuous autosync range 22 kHz to 125 kHz}
(1 5 7) with no component switching or external adjust-
ments
Y _{No manufacturing trims required internal VCO capaci-}
tor trimmed on chip
Y _{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}
transitions
Y _{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}
frequency
Y _{X-ray input disables H drive and mutes video until VCC}
powered down
Y _{H drive disabled for VCC} k _{9 5V}
Y _{Horizontal output transistor protected against accidental}
turn-on during flyback
Y _{Capacitor-programmable frequency ramping dfVCO dt}
protects H output transistor during scanning mode
changes
Connection Diagram
FIGURE 1
Order Number LM1291N
See NS Package Number N28B
C1995 National Semiconductor Corporation TL H 12323
TL H 12323 – 1
RRD-B30M115 Printed in U S A