The LM1291N 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 selection 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 LM1291N provides polarity-normalized H/HV and V sync outputs, along with logic flags which show the respective input polarities.
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 operation over the entire frequency range using just one optimized set of external
components. The system includes a second phase detector which compensates for storage time
variation in the horizontal output transistor; the picture's horizontal position is thus independent of temperature and component variance. The LM1291N provides DC control pins for H Drive duty cycle and flyback phase.
Wide continuous autosync range-22 kHz to 125 kHz (1:5.7) with no component switching or external adjustments
No manufacturing trims required-internal VCO capacitor trimmed on chip
No costly high-precision components
Low phase jitter (1.3 ns at 100 kHz)
DC controlled H phase and duty cycle
mute pulse for blanking during H frequency transitions
Input sync prioritization
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 VCC powered down
H drive disabled for VCC < 9.5V
transistor protected against accidental turn-on during flyback
Capacitor-programmable frequency ramping, dfVCO/dt, protects H output transistor during scanning mode changes
28 pin DIP. Manufactured by National.