GS1881_09 Datasheet, PDF (25/29 Pages) Gennum Corporation – Monolithic Video Sync Separators

VIDEO
INPUT
5.6k
75Ω
V_CC
5.6k
C_C
56p
-5V
8
2
4
6
680k _0.1μ
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.
COMPOSITE
SYNC OUTPUT
COMPOSITE
VIDEO INPUT
VERTICAL
SYNC OUTPUT
0.1μF
GS4981
1
8
2
7
3
6
4
5
680kW
0.1μF
V_CC 5 - 12V
HORIZONTAL
R _SET
BACK PORCH
OUTPUT
Figure 5-10: Derivation of Odd/Even with GS4981
D FLIP/FLOP
D
Q
CLK Q
ODD/EVEN
OUTPUT
GS1881, GS4881, GS4981 Monolithic Video Sync
Separators
Data Sheet
6926 - 5
November 2009
25 of 29
Proprietary & Confidential