VCC
5.6k
VIDEO
INPUT
8
2
5.6k
CC
6
4
680k
0.1μ
75Ω
56p
-5V
Figure 5-9: Typical NTSC Application Circuit
5.3 Deriving Odd/Even Using the GS4981
Odd/even field information can be derived using the vertical and horizontal outputs
from the GS4981 along with an external positive edge D flip/flop. The horizontal output
is used as the D input and the vertical output as the clock, as shown in Figure 5-10.
At the start of an odd field the vertical output ends in the middle of the horizontal line
and a high will be latched. At the start of an even field, the vertical output ends near the
beginning of the horizontal line and since the horizontal output is low, a low will be
latched. This timing sequence is shown in Figure 5-11.
GS4981
COMPOSITE
5 - 12V
D FLIP/FLOP
V
1
CC
SYNC OUTPUT
8
7
0.1μF
HORIZONTAL
COMPOSITE
VIDEO INPUT
ODD/EVEN
OUTPUT
2
D
Q
Q
680kW
0.1μF
VERTICAL
3
4
CLK
R
6
5
SYNC OUTPUT
SET
BACK PORCH
OUTPUT
Figure 5-10: Derivation of Odd/Even with GS4981
GS1881, GS4881, GS4981 Monolithic Video Sync
25 of 29
Separators
Data Sheet
Proprietary & Confidential
6926 - 5
November 2009
GENNUM [ GENNUM CORPORATION ]
