LM1292
Video PLL System for Continuous-Sync Monitors
General Description
The LM1292 is a very low jitter, integrated horizontal time
base solution specifically designed to operate in high performance,
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 LM1292
provides polarity-normalized H/HV and V sync outputs.
The LM1292 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 LM1292 provides DC control pins for H Drive duty cycle
and flyback phase.
Features
n Wide continuous autosync range—22 kHz–125 kHz
(1:5.7) with no component switching or external
adjustments
n No manufacturing trims required—internal VCO
capacitor trimmed on chip
n No costly high-precision components needed
n Very low phase jitter (below 800 ps at 125 kHz)
n DC controlled H phase and duty cycle
n Video mute pulse for blanking during H frequency
transitions
n Input sync prioritization
n Clamp pulse position and width control
n Continuous clamp pulse output, even with no sync input
n Resistor-programmable minimum and maximum VCO
frequency
n X-ray input disables H drive and mutes video until VCC
powered down
n H drive disabled for VCC < 9.5V
n Horizontal output transistor protected against accidental
turn-on during flyback
n Capacitor-programmable frequency ramping, df vco/dt,
protects H output transistor during scanning mode
changes