MAX7439ETP Maxim Integrated, MAX7439ETP Datasheet - Page 7

• Manufacturer Part Number: MAX7439ETP
• Description: Active Filter
• Manufacturer: Maxim Integrated

Specifications of MAX7439ETP

• Number Of Channels: 3
• Maximum Operating Temperature: + 85 C
• Package / Case: TQFN EP-20
• Minimum Operating Temperature: - 40 C

external resistors form a voltage-divider between V
and GND. The values in the fourth column (V
are calculated using the following equation:
where V
Apply an external voltage to HFB_ in place of R
and R
Characteristics section. Filter boost modes can also be
controlled from a microprocessor. See the Applications
Information section.
The MAX7438/MAX7439 offer selectable filter bypass-
ing that allows any of the video inputs to be filtered or
unfiltered. Select the filter bypass mode for a given
channel by setting the corresponding values for
R
The output buffer is able to drive two standard 150Ω
video loads with a 2V
buffer has a preset gain of 2V/V, and the MAX7439 out-
put buffer has a gain of 3V/V. The MAX7439 is ideal for
a DAC output whose voltage range is between 0.67V
and 1V. Set the DAC output to 0.67V to achieve a 2V/V
signal on OUT_.
The MAX7438/MAX7439 feature a back-porch clamp to
set the output blanking level. This clamp shifts the DC
level of the video signal so that the back-porch level is
close to ground (see Figure 1). The devices sense the
voltage during back porch and feed back into a control
Figure 1. Standard Video Signal
HFB_-1
Triple-Channel Video Reconstruction Filters with
V
HFB_
HFB_-2
CC
PORCH
FRONT
and R
= 5V.
= V
H-SYNC TIP
HFB_-2
as an alternative. See the Electrical
CC
_______________________________________________________________________________________
x R
COLOR BURST
according to Table 1.
HFB_-2
P-P
PORCH
BACK
signal. The MAX7438 output
/ (R
Back-Porch Clamp
HFB_-1
BLACK LEVEL (SETUP)
BLANK LEVEL
Output Buffer
+ R
Filter Bypass
HFB_-2
HFB_
HFB_-1
)
(V))
CC
Back-Porch Clamp to GND
ACTIVE VIDEO
system that provides the appropriate DC-level shift in
the filter channel to clamp the output to ground. The
back-porch clamp to ground eliminates the need for
large output-coupling capacitors that can introduce
unwanted line-time distortion (tilt), cost, and board
space. This feedback network and the on-chip capaci-
tors introduce a finite settling time (50 lines max) after
power-up or any dramatic shift in input voltage (see the
Electrical Characteristics section).
Channel 1 requires a video signal with sync information
(CVBS, Y, or G), since the other two channels are
clamped from channel 1. In the absence of a sync on
channel 1, the circuit forces all outputs actively and
continuously to ground.
The MAX7438/MAX7439 operate from dual ±5V sup-
plies. Bypass V
tors in parallel with 1µF capacitors. Place the 0.1µF
capacitors as close to the power inputs as possible.
Since EXT is a sensitive input, place R
device to avoid signals coupling into EXT. Do not route
any input, output, or dynamic signal near this pin and
the accompanying trace.
Note: The exposed paddle is electrically connected to
VSS.
Do not connect the exposed paddle to ground. Refer to
the MAX7438 EV kit for layout examples, as well as a
proven PC board layout example.
Power-Supply Bypassing and Layout
Applications Information
CC
and V
SS
to GND with 0.1µF capaci-
EXT
close to the
7