Rainbow Electronics MAX9508 - Manual (Page 18)

MAX9508
Inputs
The MAX9508 video inputs YIN, CIN, and CVBSIN
should be directly connected to the output of the video
current DAC. DC-coupling ensures that the input sig-
nals are ground referenced such that the sync tip of
composite or luma signals is within 50mV of ground
and the blank level of the chroma signal is between
0.5V and 0.65V. Since the input buffer is identical for
YIN, CIN, and CVBSIN, any standard-definition video
signal can be applied to those inputs as long as the
signal is between ground and 1.05V when V
DD = 2.7V.
For example, three composite video signals could be
applied to YIN, CIN, and CVBSIN. The RGB set and the
YPbPr set can also be inputs to YIN, CIN, and CVBSIN
(Figure 9).
The EXTCVBSIN input can only handle signals with a
sync pulse, such as composite, video, or luma.
Because the DC level of an external video input signal
is unknown, the external video signal is AC-coupled
through a 0.1µF capacitor, and a sync tip clamp sets
the internal DC level of the MAX9508. A 2:1 multiplexer
under the control of the INT/EXT input selects either the
signal at CVBSIN or EXTCVBSIN.
Video Filter Amplifier with SmartSleep and
Bidirectional Video Support
18 ______________________________________________________________________________________
CURRENT
DAC
CURRENT
DAC
CURRENT
DAC
VIDEO ENCODER
Pr/R
Pb/B
Y/G
Y/G
CIN
YIN
EXTCVBSIN
COUT
YOUT
CVBSOUT1
SHDN
INT/EXT
ACTIVE VIDEO
DETECT
SMARTSLEEP
CVBSIN
CVBSOUT2
LPF
CONTROL
LOGIC
+3.3V
+3.3V
GND
+3.3V
0.1µF
V DD
CLAMP
BUFFER
LOAD SENSE
6dB
75Ω
75Ω
LPF
BUFFER Pb/B
Y/G
Pr/R
LOAD SENSE
BUFFER
6dB
LOAD SENSE
6dB
75Ω
LOAD SENSE
6dB
75Ω
LPF
MAX9508
Figure 9. Y, Pr, Pb or RGB Set Applied to MAX9508