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MAX7444ESA+

P1-P3P4-P6P7-P8
MAX7443/MAX7444
Triple-Channel Video Reconstruction Filter and
Buffer for Composite and Y/C Outputs
4 _______________________________________________________________________________________
65
70
80
75
85
90
-40 10-15 35 60 85
SUPPLY CURRENT
vs. TEMPERATURE
MAX7443/44 toc07
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
DIFFERENTIAL GAIN
MAX7443/44 toc08
DIFFERENTIAL PHASE (DEGREES)
13245
6
7
13245
6
7
0.2
0.3
0.1
0
-0.1
-0.2
-0.3
DIFFERENTIAL GAIN (%)
0.2
0.3
0.1
0
-0.1
-0.2
-0.3
DIFFERENTIAL PHASE
MULTIBURST RESPONSE
MAX7443/44 toc09
YIN
200mV/div
YOUT
200mV/div
10µs/div
Typical Operating Characteristics (continued)
(V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
Detailed Description
The primary function of the MAX7443/MAX7444 is to fil-
ter and buffer the encoder DAC outputs that contain
digital video information in applications such as set-top
boxes, hard-disk recorders, DVD players, and digital
VCRs. These devices reconstruct and clean up analog
video signals. Each MAX7443/MAX7444 consists of a
lowpass filter and an adjustable-gain output video
buffer that is capable of driving two standard 150Ω
video loads. The luma (YIN) and chroma (CIN) video
inputs are summed internally to provide the composite
(CVOUT) video output.
These devices operate from a single +5V supply. The
filters have a nominal cutoff frequency optimized for
NTSC, PAL, and SDTV.
Filter
Filter Response
The reconstruction filter consists of two 2nd-order
Sallen-Key stages. The Butterworth-type response fea-
tures a maximally flat passband for NTSC and PAL
bandwidths. The stopband offers 41dB (typ) of attenua-
tion at sampling frequencies of 27MHz and above (see
Typical Operating Characteristics).
High-Frequency Boost
The high-frequency boost available in the MAX7444
compensates for signal degradation and rolloff in the
video encoder, which increases the image sharpness.
The MAX7443 has a flat response over the video band-
width.
Output Buffer
The output buffer drives two 150Ω video loads with a
2V
P-P
signal. The adjustable gain of the output buffer
provides a gain of 6dB, 9.5dB, and 12dB, which are
selected by tying the GSET pin to GND, V
CC
, or float-
ing, respectively. The MAX7443/MAX7444 can drive an
AC load or drive the video load directly without using
the large output capacitor. The output buffer drives a
DC load with an output blanking level of less than 1V.
PIN
NAME
FUNCTION
1 YIN Luma (Y) Input
2 GSET
Gain-Setting Control Input. See Table 1
for values.
3 CIN Chroma (C) Input
4 GND Ground
5V
CC
5V Power Supply
6
COUT
Chroma (C) Output
7
CVOUT
Composite Video Output
8
YOUT
Luma (Y) Output
Pin Description
12dB Gain Setting
The GSET pin is biased internally to V
CC
/2 through two
100kΩ resistors from V
CC
to GND. The internal imped-
ance at the node is 50kΩ. No additional connection is
necessary since the pin offers a minimum noise margin
immunity of 1V
P-P
.
Output Clamp Level
When sync pulses in the luma signal (Y) are detected,
the DC restore loop is activated. The function of the
loop is to set the sync tip of the video signal to the
desired DC level of 0.8V for YOUT and COUT and the
average DC voltage of COUT at 1.6V.
Applications Information
Input Considerations
Use a 0.1µF ceramic capacitor to AC-couple the input
to the MAX7443/MAX7444. This input capacitor stores
a DC level such that the outputs are clamped to the
appropriate DC voltage level.
Output Considerations
The outputs of the MAX7443/MAX7444 are typically
connected to a 75Ω series back-match resistor fol-
lowed by the video cable. Because of the inherent
divide by two of this configuration, the blanking level of
the video cable is always less than 1V, which complies
with industry-standard video requirements. The video
buffer can also drive an AC-coupled video load. Good
video performance is achieved with an output capacitor
as low as 220µF.
Power-Supply Bypassing and Layout
The MAX7443/MAX7444 operate from a single +5V
supply. Bypass V
CC
to GND with a 0.1µF capacitor.
Place all external components as close to the device as
possible. Refer to the MAX7443 evaluation kit for a
proven PC board layout example.
Exposed Pads
Both the SO and thin QFN packages of the MAX7443/
MAX7444 have exposed pads on the bottom of the
packages. These pads are electrically connected to
GND and should be connected to the ground plane for
improved thermal conductivity. Do not route signals
under these packages.
Chip Information
TRANSISTOR COUNT: 4252
PROCESS: BiCMOS
MAX7443/MAX7444
Triple-Channel Video Reconstruction Filter and
Buffer for Composite and Y/C Outputs
_______________________________________________________________________________________________________ 5
GSET GAIN (dB)
GND 6
V
CC
9.5
Open 12
Table 1. Gain-Setting Control
COUT
V
CC
GND
1
2
8
7
YOUT
CVOUTGSET
CIN
YIN
3
4
6
5
THIN QFN
TOP VIEW
COUT
V
CC
GND
1
2
8
7
YOUT
CVOUT
GSET
CIN
YIN
3
4
6
5
SO
MAX7443
MAX7444
MAX7443
MAX7444
Pin Configurations
Selector Guide
PART HIGH-FREQUENCY BOOST
MAX7443ETA No
MAX7443ESA No
MAX7444ETA Yes
MAX7444ESA Yes
MAX7443/MAX7444
Triple-Channel Video Reconstruction Filter and
Buffer for Composite and Y/C Outputs
6 _______________________________________________________________________________________
8L, SOIC EXP. PAD.EPS
C
1
1
21-0111
PACKAGE OUTLINE
8L SOIC, .150" EXPOSED PAD
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages
.)
P1-P3P4-P6P7-P8

MAX7444ESA+

Mfr. #:
Buy MAX7444ESA+
Manufacturer:
Maxim Integrated
Description:
IC FILTER RECON VID 8-SOIC
Lifecycle:
New from this manufacturer.
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