LM1291 National Semiconductor, LM1291 Datasheet

LM1291

Manufacturer Part Number

LM1291

Description

Video PLL System for Continuous-Sync Monitors

Manufacturer

National Semiconductor

Datasheet

1.LM1291.pdf (12 pages)

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C 1995 National Semiconductor Corporation

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

TL H 12323

See NS Package Number N28B

Order Number LM1291N

FIGURE 1

Features

Wide continuous autosync range 22 kHz to 125 kHz

(1 5 7) with no component switching or external adjust-

ments

No manufacturing trims required internal VCO capaci-

tor trimmed on chip

No costly high-precision components needed

Low phase jitter (1 3 ns at 100 kHz)

DC controlled H phase and duty cycle

Video mute pulse for blanking during H frequency

transitions

Input sync prioritization

Clamp pulse position and width control

Continuous clamp pulse output even with no sync input

Resistor-programmable minimum and maximum VCO

frequency

X-ray input disables H drive and mutes video until V

powered down

H drive disabled for V

Horizontal output transistor protected against accidental

turn-on during flyback

Capacitor-programmable frequency ramping df

protects H output transistor during scanning mode

changes

CC k

TL H 12323– 1

9 5V

RRD-B30M115 Printed in U S A

June 1995

VCO

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