19-2951; Rev 0; 8/03
4-Channel Video Filter for RGB and CVBS Video
General Description
The MAX7446 4-channel, buffered video reconstruction
filter is ideal for anti-aliasing and DAC-smoothing video
applications or wherever analog video is reconstructed
from a digital data stream (such as cable/satellite/ter-
restrial set-top boxes, DVD players, hard disk recorders
(HDRs), and personal video recorders (PVRs)). This
device operates from a single +5V supply and has a
flat passband out to 5MHz with a stopband attenuation
of 43dB at 27MHz. This makes it ideal for use with
NTSC, PAL, and standard-definition digital TV (SDTV)
video systems. Each output is capable of driving two
standard 150Ω video loads.
The MAX7446 processes CVBS and RGB video signals.
The video output buffers have a fixed gain of +6dB. The
channel for CVBS video has high-frequency boost circuitry
that provides picture sharpness with +1.2dB of gain
boost without degradation in the stopband. The output
video drivers can be disabled with an external pin.
The MAX7446 is available in a 14-pin TSSOP package
with an exposed pad, and is specified over the -40°C to
+85°C extended temperature range.
Features
o
4-Channel Filter and Buffer for RGB and
CVBS Signals
o
Filter Response Ideal for NTSC, PAL, and
Interlaced SDTV Video Signals
o
43dB (typ) Stopband Attenuation at 27MHz
o
±0.75dB (max) Passband Ripple Out to 5MHz
o
Blanking Level Voltage on Cable <1V
o
Each Channel Drives Two 150Ω Video Loads
o
+5V Single-Supply Voltage
o
Small 14-Pin TSSOP Package
MAX7446
Ordering Information
PART
MAX7446EUD
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
14 TSSOP-EP*
Applications
Set-Top Boxes/HDRs
Desktop Video Editors
Digital VCRs
Game Consoles
DVD Players
*EP
= Exposed pad.
Pin Configuration appears at end of data sheet.
Functional Diagram
V
CC
ENCODER
75Ω
0.1µF
CVBS
D/A
*
INA
LOWPASS
FILTER
SYNC
DETECTOR
OUTA
75Ω
75Ω
0.1µF
R
D/A
*
INB
LOWPASS
FILTER
OUTB
75Ω
75Ω
0.1µF
G
(WITHOUT SYNC)
D/A
INC
LOWPASS
FILTER
OUTC
75Ω
*
*
*
*
*
75Ω
75Ω
75Ω
*
75Ω
75Ω
75Ω
0.1µF
B
D/A
IND
LOWPASS
FILTER
OUTD
75Ω
75Ω
75Ω
75Ω
*OPTIONAL CAPACITORS
MAX7446
GND
DISABLE
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
4-Channel Video Filter for RGB and CVBS Video
MAX7446
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ...........................................................................+6V
All Other Pins to GND.................................-0.3V to (V
CC
+ 0.3V)
Maximum Current into Any Pin Except V
CC
and GND .....±50mA
Continuous Power Dissipation (T
A
= +70°C)
TSSOP-EP (derate 20.8mW/°C above +70°C) ...........1667mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +5V ±5%, C
L
= 0 to 20pF, R
L
= 75Ω to GND for DC-coupled load, R
L
= 75Ω to V
CC
/ 2 for AC-coupled load, C
IN_
= 0.1µF,
T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC
= +5V, T
A
= +25°C.)
PARAMETER
Passband Response
Stopband Attenuation
Differential Gain
Differential Phase
Signal-to-Noise Ratio
Group Delay Deviation
Line-Time Distortion
Field-Time Distortion
Clamp Settling Time
Output DC Clamp Level
Low-Frequency Gain Accuracy
Low-Frequency Gain Matching
Group Delay Matching
Channel-to-Channel Crosstalk
Output Short-Circuit Current
Input Leakage Current
Input Dynamic Swing
SUPPLY
Supply Voltage Range
Supply Current
Power-Supply Rejection Ratio
V
CC
I
CC
PSRR
No load
V
IN
= 100mV
P-P
, f = 0 to 3.5MHz
4.75
100
40
5.25
140
V
mA
dB
A
V
A
V(MATCH)
t
g(MATCH)
X
TALK
I
SC
I
IN
Channel A
Channels B, C, D
A
SB
dG
dθ
SNR
∆t
g
H
DIST
V
DIST
t
CLAMP
SYMBOL
CONDITIONS
f = 100kHz to 5MHz,
relative to 100kHz
f
≥
27MHz
5-step modulated staircase
5-step modulated staircase
Peak signal (2V
P-P
) to RMS noise,
f = 100Hz to 50MHz
Deviation from 100kHz
to 4.1MHz
18µs, 100 IRE bar
130 lines, 18µs, 100 IRE bar
To ±1%
Channel A
Channels B, C, D
f = 100kHz
Low-frequency channel-to-channel matching,
f = 100kHz
Low-frequency channel-to-channel matching,
f = 100kHz
f = 100kHz to 3.58MHz
OUT_ shorted to GND or V
CC
2
60
70
10
1.2
0.9
0.6
1.1
-3
0.9
1.5
Channel A
Channels B, C, D
Channel A
Channels B, C, D
MIN
0.9
-0.75
39
TYP
1.2
+0.15
43
0.15
0.15
80
17
11
30
20
0.3
0.5
100
1.1
1.8
+3
4
0.50
0.50
MAX
1.5
+0.75
UNITS
dB
dB
%
Degrees
dB
ns
%
%
Lines
V
%
%
ns
dB
mA
µA
V
P-P
2
_______________________________________________________________________________________
4-Channel Video Filter for RGB and CVBS Video
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +5V ±5%, C
L
= 0 to 20pF, R
L
= 75Ω to GND for DC-coupled load, R
L
= 75Ω to V
CC
/ 2 for AC-coupled load, C
IN_
= 0.1µF,
T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC
= +5V, T
A
= +25°C.)
PARAMETER
DISABLE
Output Impedance During Disable
Disable Logic-Input High Voltage
Disable Logic-Input Low Voltage
Disable Logic-Input Current
Z
DISABLE
V
IH
V
IL
I
DISABLE
V
IL
= 0V (sink), V
IH
= V
CC
(source)
At 5MHz
2.0
0.8
±10
2
kΩ
V
V
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX7446
Typical Operating Characteristics
(V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
AMPLITUDE vs. FREQUENCY
MAX7446 toc01
PASSBAND AMPLITUDE vs. FREQUENCY
1.5
1.0
MAX7446 toc02
PHASE RESPONSE vs. FREQUENCY
150
100
PHASE (DEGREES)
50
0
-50
-100
-150
MAX7446 toc03
2.0
HIGH-FREQUENCY BOOST
200
0
AMPLITUDE (dB)
AMPLITUDE (dB)
-20
0.5
0
-0.5
FLAT PASSBAND RESPONSE
-1.0
-1.5
-40
-60
NORMALIZED TO 0dB
-80
1
10
FREQUENCY (MHz)
100
NORMALIZED TO 0dB
-2.0
0.1
1
FREQUENCY (MHz)
10
-200
0.1
1
FREQUENCY (MHz)
10
GROUP DELAY vs. FREQUENCY
MAX7446 toc04
2T RESPONSE (1 IRE = 7.14mV)
MAX7446 toc05
MODULATED 12.5T RESPONSE
(1 IRE = 7.14mV)
MAX7446 toc06
100
90
GROUP DELAY (ns)
IN_
250mV/div
IN_
80
250mV/div
70
OUT_
OUT_
60
250mV/div
50
0.1
1
FREQUENCY (MHz)
10
200ns/div
400ns/div
250mV/div
_______________________________________________________________________________________
3
4-Channel Video Filter for RGB and CVBS Video
MAX7446
Typical Operating Characteristics (continued)
(V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
INPUTS BIASED TO +2V
NO LOAD
SUPPLY CURRENT (mA)
110
MAX7446 toc07
DIFFERENTIAL GAIN
DIFFERENTIAL PHASE (DEGREES) DIFFERENTIAL GAIN (%)
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
1st
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
1st
2nd
3rd
4th
5th
6th
2nd
3rd
4th
5th
6th
OUT_
250mV/div
MAX7446 toc08
MULTIBURST RESPONSE
MAX7446 toc09
120
IN_
250mV/div
100
DIFFERENTIAL PHASE
90
80
-40
-15
10
35
60
85
TEMPERATURE (°C)
10µs/div
Pin Description
PIN
1
2
3
4
5
6–9
10
11
12
13
14
NAME
INA
INB
INC
IND
DISABLE
GND
V
CC
OUTD
OUTC
OUTB
OUTA
FUNCTION
Channel A Video Input. Use channel A for the CVBS video signal. AC-couple INA with a series 0.1µF capacitor.
Channel B Video Input. Use channel B for the red (R) signal. AC-couple INB with a series 0.1µF capacitor.
Channel C Video Input. Use channel C for the green (G) (without sync) signal. AC-couple INC with a series
0.1µF capacitor.
Channel D Video Input. Use channel D for the blue (B) signal. AC-couple IND with a series 0.1µF capacitor.
Disable Logic Input. A logic-low on DISABLE enables the output buffers. A logic-high on DISABLE disables
all output buffers and puts them in a high-impedance state.
Ground
+5V Supply Input
Channel D Video Output. This output can be either AC- or DC-coupled.
Channel C Video Output. This output can be either AC- or DC-coupled.
Channel B Video Output. This output can be either AC- or DC-coupled.
Channel A Video Output. This output can be either AC- or DC-coupled.
Detailed Description
The MAX7446 filters and buffers video-encoder DAC
outputs in applications such as set-top boxes, hard-
disk recorders, DVD players, and digital VCRs. The
MAX7446 reconstructs and cleans up analog video sig-
nals from the output of DAC video encoders. Each
channel consists of a lowpass filter and an output video
buffer that drives two standard 150Ω video loads.
The MAX7446 is designed to process CVBS, R, G, and
B video signals. The video signal processed by chan-
nel A (CVBS) must include a sync pulse. This sync
pulse provides the required timing to all four channels.
This device operates from a single +5V supply and has
a nominal cutoff frequency of 5MHz optimized for
NTSC, PAL, and SDTV.
4
_______________________________________________________________________________________
4-Channel Video Filter for RGB and CVBS Video
Filter
Filter Response
The reconstruction filter consists of two 2nd-order Sallen-
Key stages. The Butterworth-type response features a
maximally flat passband for NTSC and PAL bandwidths.
The stopband offers at least 43dB (typ) of attenuation at
a video-encoder DAC sampling frequency of 27MHz
(see the
Typical Operating Characteristics).
High-Frequency Boost
The +1.2dB high-frequency boost on channel A increas-
es image sharpness by compensating for signal degra-
dation and roll-off in the video encoder. Channels B, C,
and D (RGB) do not boost high-frequency signals and
have a flat response over the video bandwidth.
Applications Information
Input Considerations
Use 0.1µF ceramic capacitors to AC-couple the inputs.
These input capacitors store a DC level so the outputs
are clamped to an appropriate DC voltage level.
MAX7446
Output Considerations
The outputs are typically connected to a 75Ω series
back-match resistor followed by the video cable.
Because of the inherent divide-by-two of this configura-
tion, the voltage on the video cable is always less than
1V, complying with industry-standard video require-
ments such as the European
SCART
standard (which
allows up to 2V of DC on the video cable). The video
buffer can also drive an AC-coupled video load. Good
video performance is achieved with an output capacitor
as low as 220µF.
Output Buffers
Each output buffer has a fixed gain of +6dB and can
drive two 150Ω video loads with a 2V
P-P
signal. The
MAX7446 can drive an AC load or drive the video load
directly without using a large output capacitor. The out-
put buffers drive DC loads with an output blanking level
of less than 1V.
Power-Supply Bypassing and Layout
The MAX7446 operates 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.
Output Clamp Level
When a sync pulse is detected on channel A, the DC
restore loop is activated. The function of the loop is to
set the DC value of the video signal to a specified volt-
age. See Table 1 for clamp levels.
Exposed Pads
The TSSOP-EP package has an exposed pad on the
bottom of the package. This pad is electrically connect-
ed to GND and should be connected to the ground
plane for improved thermal conductivity. Do not route
signals under this package.
Table 1. Output Clamp Level
CHANNEL
A
B
C
D
CLAMP LEVEL (V)
0.8
1.4
1.4
1.4
Pin Configuration
TOP VIEW
INA 1
INB
INC
2
3
14 OUTA
13 OUTB
12 OUTC
IND 4
DISABLE 5
GND 6
GND 7
MAX7446
11 OUTD
10 V
CC
9
8
GND
GND
TSSOP
Chip Information
TRANSISTOR COUNT: 6300
PROCESS: BiCMOS
_______________________________________________________________________________________
5
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