max9508atet Maxim Integrated Products, Inc., max9508atet Datasheet - Page 12

• Manufacturer Part Number: max9508atet
• Description: Max9508 Video Filter Amplifier With Smartsleep And Bidirectional Video Support
• Manufacturer: Maxim Integrated Products, Inc.

The active video detect circuit slices the CVBSIN signal
at 4.7% of the power supply (155mV for a 3.3V supply).
If the transitions occur at a rate of 14.3kHz or higher, a
video signal is present. When the MAX9508 detects a
video signal with sync at the CVBSIN input, the control
logic enters the active-detect mode and enables the
load sense circuitry
typically 17µA.
CVBS/S-Video Filter Amplifier with
SmartSleep and Bidirectional Video Support
Figure
12
______________________________________________________________________________________
3. Active-Detect Mode with No Output Loads
VIDEO ENCODER
CURRENT
CURRENT
CURRENT
50mV
DAC
DAC
DAC
TO
VIDEO SIGNAL
0
PRESENT
(Figure
+3.3V
+3.3V
SMARTSLEEP
3). The supply current is
EXTCVBSIN
INT/EXT
CVBSIN
SHDN
Active-Detect Mode
CIN
YIN
CLAMP
OFF
BUFFER
BUFFER
ACTIVE VIDEO
OFF
OFF
CONTROL
DETECT
LOGIC
BUFFER
OFF
17μA
LPF
LPF
LPF
OFF
OFF
OFF
MAX9508
+3.3V
If an output load is not connected to any amplifier, the
MAX9508 remains in active detect mode. Eight times per
second, each load-sense circuit checks for a load by
connecting an internal 15kΩ pullup resistor to the output
for 1ms. If the output is pulled up, then no load is pre-
sent. If the output stays low, a load is connected.
GND
V
DD
6dB
6dB
6dB
6dB
OFF
OFF
OFF
OFF
LOAD SENSE
LOAD SENSE
LOAD SENSE
LOAD SENSE
YOUT
CVBSOUT1
CVBSOUT2
COUT
75Ω
75Ω
75Ω
75Ω
SVIDEO
CHROMA
SVIDEO
LUMA
CVBS 1
CVBS 2
NO
LOADS