MAX9507 Maxim Integrated Products, MAX9507 Datasheet - Page 25

• Manufacturer Part Number: MAX9507
• Description: 1.8V DirectDrive Video Filter Amplifier
• Manufacturer: Maxim Integrated Products

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The MAX9507 can also provide anti-alias filtering with a
buffer before an analog-to-digital converter (ADC),
which would be present in an NTSC/PAL video decoder,
for example. Figure 18 shows the application circuit. An
external composite video signal is applied to VIDIN,
which is terminated with a total of 74Ω (56Ω and 18Ω
resistors) to ground. The signal is attenuated by four,
and then AC-coupled to IN. The normal 1V
nal must be attenuated because with a 1.8V supply, the
MAX9507 can only handle a video signal of approxi-
Figure 18. MAX9507 Used as an Anti-Alias Filter with Buffer
Load Detection and Dual SPST Analog Switches
MICROCONTROLLER
1.8V DirectDrive Video Filter Amplifier with
56Ω
18Ω
VIDIN
______________________________________________________________________________________
10Ω
1.8V
0.1μF
C3
V
Anti-Alias Filter
CC
0.1μF
P-P
NO1
NO2
SDA
SCL
LCF
V
video sig-
DD
IN
TRANSPARENT
CLAMP
MAX9507
CPGND
mately 0.25V
because the DC level of an external video signal is usu-
ally not well specified, although it is reasonable to
expect that the signal is between -2V and +2V. The 10Ω
series resistor increases the equivalent source resis-
tance to about 25Ω, which is the minimum necessary for
a video source to drive the internal sync-tip clamp.
For external video signals larger than 1V
ate the MAX9507 from a 2.5V supply so that IN can
accommodate a 0.325V
alent to a 1.3V
LPF
I
2
C1P
C INTERFACE
CHARGE PUMP
1μF
LEVEL SHIFT
C1
C1N
DC
SW1
SW2
P-P
REGULATOR
V
P-P
LINEAR
SS
A
at IN. AC-couple the video signal to IN
V
video signal at VIDIN.
= 8V/V
C2
1μF
V
DD
DETECT
LOAD
P-P
video signal, which is equiv-
COM1
COM2
OUT
GND
75Ω
P-P
, then oper-
25