The EL4583 extracts timing from video sync in NTSC, PAL,
and SECAM systems, and non standard formats, or from
computer graphics operating at higher scan rates. Timing
adjustment is via an external resistor. Input without valid
vertical interval (no serration pulses) produces a default
vertical output.
Outputs are: composite sync, vertical sync, filter, burst/back
porch, horizontal, no signal detect, level, and odd/even
output (in interlaced scan formats only).
The EL4583 sync slice level is set to the mid-point between
sync tip and the blanking level. This 50% point is determined
by two internal sample and hold circuits that track sync tip
and back porch levels. It provides hum and noise rejection
and compensates for input levels of 0.5V to 2.0VP-P.
A built in filter attenuates the chroma signal to prevent color
burst from disturbing the 50% sync slice. Cut off frequency is
set by a resistor to ground from the Filter Cut Off pin.
Additionally, the filter can be by-passed and video signal fed
directly to the Video Input.
The level output pin provides a signal with twice the sync
amplitude which may be used to control an external AGC
function. A TTL/CMOS compatible No Signal Detect Output
flags a loss or reduction in input signal level. A resistor sets
the Set Detect Level.