The EL4581 extracts timing
information from standard negative
going video sync found in NTSC, PAL
and SECAM broadcast systems. It can also be used in non
standard formats and with computer graphics systems at
higher scan rates, by adjusting a single external resistor.
When the input does not have correct serration pulses in the
vertical interval, a default vertical output is produced.
Outputs are composite sync, vertical sync, burst/back porch
output, and odd/even output. The later operates only in
interlaced scan formats.
The EL4581 provides a reliable method of determining
correct sync slide level by setting it to the mid-point between
sync tip and blanking level at the back porch. This 50% level
is determined by two internal self timing sample and hold
circuits that track sync tip and back porch levels. This also
provides a degree of hum and noise rejection to the input
signal, and compensates for varying input levels of 0.5VP-P
to 2.0VP-P.
A built in linear phase, third order, low pass filter attenuates
the chroma signal in color systems to prevent incorrectly set
color burst from disturbing the 50% sync slide.
This device may be used to replace the industry standard
LM1881, offering improved performance and reduced power
consumption.
The EL4581 video sync separator is manufactured using
Elantec’s high performance analog CMOS process.