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 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 LM1291
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 LM1291 provides DC control pins for H Drive duty cycle