Burst/Black Level

Gate Time vs R

SET

Vertical Pulse

Width vs R

SET

00915009

00915010

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

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-

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 Figure 1(a-e) 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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