GS1881, GS4881, GS4981
Monolithic Video Sync Separators
DATA SHEET
FEATURES
DESCRIPTION
• noise tolerant odd/even flag, back porch and
horizontal sync pulse
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.
• 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
• Pb-free and Green
• 5 V to 12 V supply voltage range
• pin compatible with LM1881 sync separator
SELECTION CHART
APPLICATION
CHOOSE DEVICE:
Direct LM1881 Replacement
with Improved Performance
GS1881
New Applications
Substitution for LM1881
GS4881
New Applications Requiring
Horizontal Sync Output
GS4981
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.
PIN CONNECTIONS
GS4981
GS1881, GS4881
COMPOSITE
SYNC OUT
8
1
V
cc
COMPOSITE
VIDEO IN
2
7
ODD/EVEN
VERTICAL
SYNC OUT
3
6
RSET
GROUND
4
5
BACK PORCH
COMPOSITE
SYNC OUT
1
8
V
COMPOSITE
VIDEO IN
2
7
HORIZONTAL
VERTICAL
SYNC OUT
3
6
RSET
GROUND
4
5
BACK PORCH
8 PIN DIP
8 PIN SOIC
cc
8 PIN DIP
8 PIN SOIC
Patent No. 5,432,559
Revision Date: July 2004
Document No. 520 - 23 - 04
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-5946
Gennum Japan: Shinjuku Green Tower Building 27F 6-14-1, Nishi Shinjuku Shinjuku-ku, Tokyo 160-0023 Japan
Tel: +81 (03) 3349-5501
Fax: +81 (03) 3349-5505
