Datasheet

AD8143
Rev. 0 | Page 23 of 24
where:
The AD8134 encoding equations are given in Equation 3,
Equation 4, and Equation 5.
[]
(3)
Red V
CM
, Green V
CM
, and Blue V
CM
are the transmitted common-
mode voltages of the respective color signals.
HV
K
VRed
CM
−=
2
[
V2
2
−=
K
VGreen
CM
]
(4)
K is a an adjustable gain constant that is set by the
AD8134.
[
HV
K
VBlue
CM
+=
2
]
(5)
V and H are the vertical and horizontal sync pulses, defined
with a weight of −1 when the pulses are in their low states, and a
weight of +1 when they are in their high states.
The
AD8134 data sheet contains further details regarding the
encoding scheme.
Figure 48 illustrates how the AD8143 comparators can be used
to extract the horizontal and vertical sync pulses that are
encoded on the RGB common-mode voltages by the
AD8134.
05538-057
RECEIVED RED VIDEO
HSYNC
RED CMV
GREEN CMV
BLUE CMV
50Ω
50Ω
1kΩ
1kΩ
VSYNC
RECEIVED GREEN VIDEO
50Ω
50Ω
RECEIVED BLUE VIDEO
50Ω
50Ω
Figure 48. Extracting Sync Signals from Received Common-Mode Signals