LM1881, LM1881-X
Typical Performance Characteristics
Burst/Black Level
Gate Time vs R
SET
(Continued)
Vertical Pulse
Width vs R
SET
00915010
00915009
Vertical Pulse
Width vs Temperature
Supply Current vs
Supply Voltage
00915011
00915002
Application Notes
The LM1881 is designed to strip the synchronization signals
from composite video sources that are in, or similar to, the
N.T.S.C. format. Input signals with positive polarity video
(increasing signal voltage signifies increasing scene bright-
ness) from 0.5V (p-p) to 2V (p-p) can be accommodated.
The LM1881 operates from a single supply voltage between
5V DC and 12V DC. The only required external components
besides a power supply decoupling capacitor at pin 8 and a
set current decoupling capacitor at pin 6, are the composite
input coupling capacitor at pin 2 and one resistor at pin 6 that
sets internal current levels. The resistor on pin 6 (i.e. R
set
)
allows the LM1881 to be adjusted for source signals with line
scan frequencies differing from 15.734 kHz. Four major sync
signals are available from the I/C; composite sync including
both horizontal and vertical scan timing information; a verti-
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cal sync pulse; a burst gate or back porch clamp pulse; and
an odd/even output. The odd/even output level identifies
which video field of an interlaced video source is present at
the input. The outputs from the LM1881 can be used to
gen-lock video camera/VTR signals with graphics sources,
provide identification of video fields for memory storage,
recover suppressed or contaminated sync signals, and pro-
vide timing references for the extraction of coded or uncoded
data on specific video scan lines.
To better understand the LM1881 timing information and the
type of signals that are used, refer to
which
shows a portion of the composite video signal from the end
of one field through the beginning of the next field.
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