19-3560; Rev 0; 1/05
Video Switch for Dual SCART Connectors
General Description
The MAX7457 4-channel video switch is ideal for anti-
aliasing and DAC-smoothing video applications or wher-
ever analog video is reconstructed from a digital data
stream such as cable/satellite/terrestrial set-top boxes
(STBs), DVD players, hard disk recorders (HDRs), and
personal video recorders (PVRs). The MAX7457 filters
and buffers CVBS and RGB video signals, making it
ideal for dual SCART (peritelevision) STBs with an
auxiliary CVBS input. The MAX7457 operates from a sin-
gle +5V supply and has a flat passband out to 5MHz
with a stopband attenuation of 43dB at 27MHz, making
it ideal for NTSC, PAL, and standard-definition digital TV
(SDTV) video systems.
The MAX7457 output buffers have a fixed gain of +6dB
and are capable of driving two standard 150Ω video
loads. The channel for CVBS video has high-frequency
boost circuitry that enhances picture sharpness with up
to +1.2dB of gain boost without degradation in the
stopband. The video output drivers can be disabled by
an external control input.
The MAX7457 is available in a 16-pin, 5mm x 5mm x
0.8mm TQFN package, and is specified over the
extended (-40°C to +85°C) temperature range.
Features
♦
4-Channel Video Filter/Buffer for RGB and CVBS
Signals with Auxiliary Input
♦
Allows Auxiliary Input for CVBS Video Loop-
Through Applications
♦
Filter Response Ideal for NTSC, PAL, and
Interlaced SDTV Video Signals
♦
43dB (typ) Stopband Attenuation at 27MHz
♦
±0.75dB (max) Passband Ripple Out to 5MHz
♦
Blanking Level Voltage on Cable <1V
♦
Each Channel Drives Two 150Ω Video Loads
♦
+5V Single-Supply Operation
♦
Available in 5mm x 5mm x 0.8mm, 16-Pin TQFN
MAX7457
Ordering Information
PART
MAX7457ETE
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 TQFN-EP*
PKG
CODE
T1655-2
Applications
STBs/HDRs
Game Consoles
Desktop Video Editors
DVD Players
Digital VCRs
*EP
= Exposed pad.
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
V
CC
SELA
0.1µF
INA2
0.1µF
2-TO-1
MUX
LOWPASS
FILTER
SYNC
DETECTOR
+6dB
OUTA
75Ω
*
75Ω
75Ω
*
75Ω
AUXILIARY VIDEO SOURCE
(VCR, DVD, ETC.)
ENCODER
CVBS D/A
INA1
75Ω
0.1µF
R D/A
INB
LOWPASS
FILTER
+6dB
OUTB
75Ω
*
75Ω
*
75Ω
75Ω
0.1µF
G D/A
INC
LOWPASS
FILTER
+6dB
OUTC
75Ω
*
75Ω
*
75Ω
75Ω
0.1µF
B D/A
IND
LOWPASS
FILTER
+6dB
OUTD
75Ω
*
75Ω
*
75Ω
MAX7457
GND
DISABLE
*OPTIONAL CAPACITORS
________________________________________________________________
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.
Video Switch for Dual SCART Connectors
MAX7457
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..............................................................-0.3V to +6V
INA1, INA2, INB, INC, IND to GND ............-0.3V to (V
CC
+ 0.3V)
OUTA, OUTB, OUTC, OUTD to GND .........-0.3V to (V
CC
+ 0.3V)
SELA, DISABLE 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)
16-Pin TQFN (derate 20.8mW/°C
above +70°C)..........................................................1666.7mW
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, T
A
= T
MIN
to
T
MAX
, unless otherwise noted. Typical values are at V
CC
= 5V, T
A
= +25°C.)
PARAMETER
Passband Flatness
Stopband Attenuation
Differential Gain
Differential Phase
Signal-to-Noise Ratio
A
SB
dG
dθ
SNR
SYMBOL
CONDITIONS
Channel INA_
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
Channel INA_
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
Disabled Output Impedance
Output Short-Circuit Current
A
V
A
V(MATCH)
t
g(MATCH)
X
TALK
Z
DISABLE
I
SC
∆t
g
H
DIST
V
DIST
t
CLAMP
Deviation from
100kHz to 4.1MHz
18µs, 100 IRE bar
130 lines, 18µs, 100 IRE bar
To ±1%
Channel INA_
Channel INB, INC, IND
f = 100kHz, relative to gain of +6dB
Low-frequency channel-to-channel
matching, f = 100kHz
Low-frequency channel-to-channel
matching, f = 100kHz
f = 100kHz to 3.58MHz
At 5MHz
OUT_ shorted to GND or V
CC
2
-60
2
70
0.6
1.1
-3
300
0.9
1.5
1.1
1.8
+3
4
Channels INB,
INC, IND
Channels INB,
INC, IND
MIN
+0.9
-0.75
40
TYP
+1.2
+0.15
43
0.15
0.15
80
17
11
30
20
0.3
0.5
ns
%
%
Lines
V
%
%
ns
dB
kΩ
mA
0.5
0.5
MAX
+1.5
+0.75
dB
dB
%
Degrees
dB
UNITS
2
_______________________________________________________________________________________
Video Switch for Dual SCART Connectors
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, T
A
= T
MIN
to
T
MAX
, unless otherwise noted. Typical values are at V
CC
= 5V, T
A
= +25°C.)
PARAMETER
Input Leakage Current
Input Dynamic Swing
Mux Crosstalk
SUPPLY
Supply Voltage Range
Supply Current
Power-Supply Rejection Ratio
LOGIC INTERFACE
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
V
IH
V
IL
V
IL
= 0 (sink), V
IH
= V
CC
(source)
2.0
0.8
±10
V
V
µA
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
SYMBOL
I
IN
Channel INA_
Channels INB, INC, IND
f = 100kHz to 4.1MHz
-60
CONDITIONS
MIN
TYP
MAX
10
1.2
0.9
UNITS
µA
V
P-P
dB
MAX7457
Typical Operating Characteristics
(V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
AMPLITUDE vs. FREQUENCY
MAX7457 toc01
PASSBAND AMPLITUDE vs. FREQUENCY
1.5
1.0
CHANNEL INA_
MAX7457 toc02
PHASE RESPONSE vs. FREQUENCY
150
100
PHASE (DEGREES)
50
0
-50
-100
-150
-200
MAX7457 toc03
2.0
200
0
AMPLITUDE (dB)
AMPLITUDE (dB)
-20
0.5
0
-0.5
CHANNELS INB/INC/IND
-1.0
-40
-60
CHANNEL INA_
-80
1
10
FREQUENCY (MHz)
100
-1.5
-2.0
0.1
1
FREQUENCY (MHz)
10
0.1
1
FREQUENCY (MHz)
10
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3
Video Switch for Dual SCART Connectors
MAX7457
Typical Operating Characteristics (continued)
(V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
GROUP DELAY vs. FREQUENCY
MAX7457 toc04
2T RESPONSE
(1 IRE = 7.14mV)
MAX7457 toc05
MODULATED 12.5T RESPONSE
(1 IRE = 7.14mV)
MAX7457 toc06
100
90
GROUP DELAY (ns)
80
70
60
50
40
0.1
1
FREQUENCY (MHz)
IN_
300mV/div
IN_
300mV/div
OUT_
300mV/div
OUT_
300mV/div
10
200ns/div
400µs/div
DIFFERENTIAL GAIN (%)
SUPPLY CURRENT vs. TEMPERATURE
MAX7457 toc07
DIFFERENTIAL GAIN
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
1
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
1
2
3
4
5
6
7
2
3
4
5
6
7
MAX7457 toc08
MULTIBURST RESPONSE
MAX7457 toc09
120
INPUTS BIASED TO +2V
NO LOAD
SUPPLY CURRENT (mA)
110
IN_
250mV/div
100
DIFFERENTIAL PHASE
(DEGREES)
DIFFERENTIAL PHASE
OUT_
250mV/div
90
80
-40
-15
10
35
60
85
TEMPERATURE (°C)
10µs/div
4
_______________________________________________________________________________________
Video Switch for Dual SCART Connectors
Pin Description
PIN
1
2
3
4
5
6, 8, 14
7
9
10
11
12
13
15
16
—
NAME
INB
INC
IND
DISABLE
SELA
N.C.
GND
V
CC
OUTD
OUTC
OUTB
OUTA
INA2
INA1
EP
FUNCTION
Channel INB Video Input. Use channel INB for the red (R) signal. AC-couple INB with a series
0.1µF capacitor.
Channel INC Video Input. Use channel INC for the green (G) signal. AC-couple INC with a series
0.1µF capacitor.
Channel IND Video Input. Use channel IND 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 buffer outputs and puts them in a high-impedance state.
Select A Input. A logic low on SELA selects INA1 and a logic high on SELA selects INA2.
No Connection. Not internally connected.
Ground
+5V Supply Input
Channel D Video Output. OUTD can be either AC- or DC-coupled.
Channel C Video Output. OUTC can be either AC- or DC-coupled.
Channel B Video Output. OUTB can be either AC- or DC-coupled.
Channel A Video Output. OUTA can be either AC- or DC-coupled.
Channel INA2 Video Input. Connect auxiliary CVBS to INA2. AC-couple INA2 with a series
0.1µF capacitor.
Channel INA1 Video Input. Connect CVBS to INA1. AC-couple INA1 with a series 0.1µF capacitor.
Exposed Pad. Connect to GND for improved thermal heat sinking.
MAX7457
Detailed Description
The MAX7457 4-channel video switch filters and
buffers video encoder DAC outputs in applications
such as STBs, HDRs, DVD players, and digital VCRs.
The MAX7457 offers an auxiliary CVBS loop-through
feature required in dual SCART applications. Audio and
video switching in SCART STBs utilize a costly integrat-
ed A/V switch offering high-end features such as vol-
ume control and high audio-drive capability. A more
cost-effective solution uses the MAX7457 for the video
switching along with low-cost standard passive analog
switches for the audio switching.
The MAX7457 reconstructs and cleans up analog video
signals from the video encoder’s DAC output. Each
channel consists of a lowpass filter and an output video
buffer that drives two standard 150Ω video loads. The
MAX7457 operates from a single +5V supply and has a
nominal cutoff frequency of 5MHz, 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 at least 43dB (typ) of
attenuation at the video encoder’s DAC sampling fre-
quency of 27MHz (see the
Typical Operating
Characteristics).
High-Frequency Boost
INA1/INA2 have +1.2dB of high-frequency boost that
increases image sharpness by compensating for sig-
nal degradation and rolloff in the video encoder.
Channels INB/INC/IND (RGB) do not boost high-fre-
quency signals and have a flat response over the
video bandwidth.
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