GS1881, GS4881, GS4981
Monolithic Video Sync Separators
DATA SHEET
FEATURES
• noise tolerant odd/even flag, back porch and
horizontal sync pulse
• fast recovery from impulse noise
• excellent temperature stability
• 0.5 V to 4 Vpp input signal amplitude with 5 V
supply
• well-controlled clamp discharge current and
slicing level
• programmable horizontal scan rate (up to 130 kHz)
• composite, vertical, back porch, odd/even
(GS1881, GS4881), horizontal (GS4981) outputs
• predictable vertical output pulse width with
default trigger for non-standard video signals
• 5 V to 12 V supply voltage range
• pin compatible with LM1881 sync separator
SELECTION CHART
DESCRIPTION
The GS1881, GS4881 and GS4981 are general purpose sync
separators for use in a wide variety of video applications. The
devices extract the timing information from composite video
signals with scan rates from 15 to 130 kHz.
The GS1881 is a drop-in replacement for the industry standard
LM1881 with much improved performance. The device
generates composite sync, vertical sync, back porch and
odd/even field signals. The GS4881 is identical to the GS1881
but features a noise immune back porch pulse which maintains
a constant H rate during the vertical interval. The GS4981 is
identical to the GS4881, except that it provides horizontal sync
in place of the odd/even output.
All three devices feature a self-adjusting windowing circuit for
noise immunity, which synchronizes to H rate. This
windowing c i r c u i t d e t e r m i n e s t h e o d d o r e v e n f i e l d
in the GS1881 and GS4881, gates the back porch pulse in
the GS4881 and GS4981, and generates the horizontal sync
output in the GS4981.
The devices feature an improved input stage which ensures
that the input signal is sliced at a predictable point due to
well-controlled input clamp discharge current and sync
slicing level. A missing pulse detector enables the devices to
recover quickly from impulse noise disturbances by temporarily
increasing the clamp discharge current by roughly ten times.
The input stage will operate with signals from 0.5 to 4 volts
peak to peak with a 5 volt supply.
The GS1881, GS4881 and GS4981 also feature a predictable
vertical output pulse width with a default trigger for non-standard
video signals. All three are available in commercial and
industrial temperature ranges and are packaged in both DIP
and SOIC.
APPLICATION
Direct LM1881 Replacement
with Improved Performance
New Applications
Substitution for LM1881
New Applications Requiring
Horizontal Sync Output
CHOOSE DEVICE:
GS1881
GS4881
GS4981
PIN CONNECTIONS
GS1881, GS4881
COMPOSITE
SYNC OUT
COMPOSITE
VIDEO IN
VERTICAL
SYNC OUT
GROUND
1
2
3
4
8
7
6
5
V
COMPOSITE
SYNC OUT
COMPOSITE
VIDEO IN
VERTICAL
SYNC OUT
GROUND
1
2
3
4
GS4981
8
7
6
5
V
cc
cc
ODD/EVEN
R
SET
BACK PORCH
HORIZONTAL
R
SET
BACK PORCH
8 PIN DIP
8 PIN SOIC
Patent No. 5,432,559
Revision Date: October 1995
8 PIN DIP
8 PIN SOIC
Document No. 520 - 23 - 03
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-2055
Japan Branch: A-302 Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168, Japan
tel. (03) 3247-8838
fax (03) 3247-8839
GENNUM [ GENNUM CORPORATION ]
