MAXIM MAX7445

19-2948; Rev 0; 8/03
4-Channel Video Reconstruction Filter
Features
♦ 4-Channel Filter and Buffer for CVBS, RGB, or Y/C
Video Signals
The MAX7445 has three modes of operation. Mode 1
processes CVBS and RGB video signals. Mode 2
processes CVBS, Y, and C signals, as well as a second
asynchronous CVBS video signal. Mode 3 processes
RGB and CVBS (asynchronous) video signals. An external pin adjusts the gain of the video buffer to either +6dB,
+9.5dB, or +12dB to accommodate video-encoder DAC
output signals of <1V. High-frequency boost circuitry 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.
♦ 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 Voltage
♦ Selectable Gain: +6dB, +9.5dB, and +12dB
♦ Small 14-Pin TSSOP Package
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX7445EUD
-40°C to +85°C
14 TSSOP-EP*
*EP = Exposed pad.
The MAX7445 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.
Applications
Set-Top Boxes/HDRs
Game Consoles
DVD Players
Digital VCRs
Pin Configuration appears at end of data sheet.
Desktop Video Editors
Functional Diagram
VCC
ENCODER
75Ω
0.1µF
D/A
75Ω
*
INA
LOWPASS
FILTER
OUTA
SYNC
DETECTOR
75Ω
*
75Ω
0.1µF
D/A
75Ω
*
INB
LOWPASS
FILTER
OUTB
LOWPASS
FILTER
OUTC
75Ω
75Ω
0.1µF
INC
D/A
75Ω
75Ω
*
*
*
75Ω
75Ω
75Ω
SELECT
MAX7445
75Ω
0.1µF
D/A
IND
LOWPASS
FILTER
OUTD
SYNC
DETECTOR
75Ω
*
*
75Ω
75Ω
*OPTIONAL CAPACITORS
GND
DISABLE
GAIN
________________________________________________________________ Maxim Integrated Products
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.
1
MAX7445
General Description
The MAX7445 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/terrestrial 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.
MAX7445
4-Channel Video Reconstruction Filter
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................................+6V
All Other Pins to GND.................................-0.3V to (VCC + 0.3V)
Maximum Current into Any Pin Except VCC and GND .....±50mA
Continuous Power Dissipation (TA = +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
(VCC = +5V ±5%, CL = 0 to 20pF, RL = 75Ω to GND for DC-coupled load, RL = 75Ω to VCC / 2 for AC-coupled load, CIN_ = 0.1µF,
GAIN = GND (+6dB) or VCC (+9.5dB), TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
f = 100kHz to 5MHz,
relative to 100kHz
Passband Response
Stopband Attenuation
ASB
f ≥ 27MHz
Differential Gain
dG
5-step modulated
staircase
Differential Phase
Signal-to-Noise Ratio
Group Delay Deviation
dθ
5-step modulated
staircase
SNR
Peak signal (2VP-P) to
RMS noise,
f = 100Hz to 50MHz
∆tg
Deviation from 100kHz
to 4.1MHz
MIN
TYP
MAX
Channel without
boost (see Table 2)
-0.75
+0.15
+0.75
Channel with boost
(see Table 2)
+0.9
+1.2
+1.5
39
43
UNITS
dB
dB
Gain = +6dB,
+9.5dB
0.15
0.50
Gain = +12dB
0.25
0.90
Gain = +6dB,
+9.5dB
0.15
0.50
Gain = +12dB
0.15
0.60
Gain = +6dB,
+9.5dB, +12dB
69
Channel without
boost (see Table 2)
75
11
%
Degrees
dB
20
ns
Channel with boost
(see Table 2)
17
30
Line-Time Distortion
HDIST
18µs, 100 IRE bar
0.3
Field-Time Distortion
VDIST
130 lines, 18µs, 100 IRE bar
0.5
%
Clamp Settling Time
tCLAMP
To ±1%
100
Lines
SELECT = GND
Output DC Clamp Level
SELECT = VCC
SELECT = floating
Low-Frequency Gain Accuracy
AV
Low-Frequency Gain Matching
AV(MATCH)
2
Channel A
0.6
0.9
1.1
Channels B, C, D
1.1
1.5
1.8
Channels A, B, D
0.6
0.9
1.1
Channel C
1.25
1.6
1.95
Channels A, D
0.6
0.9
1.1
Channels B, C
1.1
1.5
1.8
f = 100kHz, relative to a gain of +6dB
-3
Low-frequency channel-to-channel matching,
f = 100kHz
_______________________________________________________________________________________
%
V
+3
%
4
%
4-Channel Video Reconstruction Filter
(VCC = +5V ±5%, CL = 0 to 20pF, RL = 75Ω to GND for DC-coupled load, RL = 75Ω to VCC / 2 for AC-coupled load, CIN_ = 0.1µF,
GAIN = GND (+6dB) or VCC (+9.5dB), TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V, TA = +25°C.)
PARAMETER
Group Delay Matching
Channel-to-Channel Crosstalk
SYMBOL
CONDITIONS
tg(MATCH)
Low-frequency channel-to-channel matching,
f = 100kHz
2
ns
f = 100kHz to 3.58MHz
60
dB
OUT_ shorted to GND or VCC
70
XTALK
Output Short-Circuit Current
ISC
Input Leakage Current
IIN
TYP
MAX
SELECT = VCC
SELECT = floating
Channel A
UNITS
mA
10
SELECT = GND
Input Dynamic Swing for Gain
of +6dB
MIN
µA
1.2
Channels B, C, D
0.9
Channels A, B, D
1.2
Channel C
0.9
Channels A, D
1.2
Channels B, C
0.9
VP-P
SUPPLY
Supply Voltage Range
VCC
Supply Current
ICC
Power-Supply Rejection Ratio
PSRR
4.75
5.25
V
140
mA
No load
100
VIN = 100mVP-P, f = 0 to 3.5MHz
40
dB
At 5MHz
2
kΩ
DISABLE
Output Impedance During
Disable
Disable Logic-Input High Voltage
Disable Logic-Input Low Voltage
Disable Logic Input Current
ZDISABLE
VIH
2.0
VIL
IDISABLE
VIL = 0V (sink), VIH = VCC (source)
V
0.8
V
±10
µA
_______________________________________________________________________________________
3
MAX7445
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = +5V, VGAIN = 0V, TA = +25°C, unless otherwise noted.)
PASSBAND AMPLITUDE vs. FREQUENCY
0
1.5
PHASE RESPONSE vs. FREQUENCY
200
MAX7445 toc02
MAX7445 toc01
2.0
HIGH-FREQUENCY BOOST
150
100
-40
PHASE (DEGREES)
AMPLITUDE (dB)
AMPLITUDE (dB)
1.0
-20
0.5
0
-0.5
FLAT PASSBAND RESPONSE
-1.5
NORMALIZED TO 0dB
-150
-200
-2.0
10
100
0.1
1
0.1
10
FREQUENCY (MHz)
FREQUENCY (MHz)
GROUP DELAY vs. FREQUENCY
2T RESPONSE (1 IRE = 7.14mV)
MAX7445 toc04
90
80
10
1
FREQUENCY (MHz)
MODULATED 12.5T RESPONSE
(1 IRE = 7.14mV)
MAX7445 toc06
MAX7445 toc05
100
GROUP DELAY (ns)
0
-50
NORMALIZED TO 0dB
-80
1
50
-100
-1.0
-60
MAX7445 toc03
AMPLITUDE vs. FREQUENCY
IN_
IN_
250mV/
div
250mV/
div
OUT_
OUT_
250mV/
div
250mV/
div
70
60
50
0.1
200ns/div
400ns/div
DIFFERENTIAL GAIN
MULTIBURST RESPONSE
10
1
FREQUENCY (MHz)
110
100
90
80
-40
-15
10
35
TEMPERATURE (°C)
4
60
85
MAX7445 toc09
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
MAX7445 toc08
MAX7445 toc07
INPUTS BIASED TO +2V
NO LOAD
DIFFERENTIAL PHASE (DEGREES) DIFFERENTIAL GAIN (%)
SUPPLY CURRENT vs. TEMPERATURE
120
SUPPLY CURRENT (mA)
MAX7445
4-Channel Video Reconstruction Filter
1st
2nd
3rd
4th
5th
6th
IN_
250mV/
div
DIFFERENTIAL PHASE
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
OUT_
250mV/
div
1st
2nd
3rd
4th
5th
6th
10µs/div
_______________________________________________________________________________________
4-Channel Video Reconstruction Filter
PIN
NAME
1
INA
Channel A Video Input. AC-couple INA with a series 0.1µF capacitor.
2
INB
Channel B Video Input. AC-couple INB with a series 0.1µF capacitor.
3
INC
Channel C Video Input. AC-couple INC with a series 0.1µF capacitor.
4
IND
Channel D Video Input. AC-couple IND with a series 0.1µF capacitor.
5
6, 8
FUNCTION
Disable Logic Input. A logic-low on DISABLE enables the output buffers. A logic-high on DISABLE disables
DISABLE
all output buffers and puts them in a high-impedance state.
GND
Ground
7
GAIN
Gain-Control Input. Connect GAIN to GND for a gain of +6dB (+2V/V), to VCC for a gain of +9.5dB (+3V/V),
or leave unconnected for a gain of +12dB (+4V/V).
9
SELECT
10
VCC
11
OUTD
12
OUTC
Channel C Video Output. This output can be either AC- or DC-coupled.
13
OUTB
Channel B Video Output. This output can be either AC- or DC-coupled.
14
OUTA
Channel A Video Output. This output can be either AC- or DC-coupled.
Mode Select Input. Connect to GND for CVBS/RGB processing, to VCC for CVBS/Y/C/CVBSASYNC
processing, or leave floating for RGB/CVBSASYNC (G with sync) processing.
+5V Supply Input
Channel D Video Output. This output can be either AC- or DC-coupled.
Detailed Description
The MAX7445 filters and buffers video-encoder DAC
outputs in applications such as set-top boxes, harddisk recorders, DVD players, and digital VCRs. The
MAX7445 reconstructs and cleans up analog video signals from the output of DAC video encoders. Each
channel consists of a lowpass filter and an output video
buffer that can drive two standard 150Ω video loads.
This device operates from a single +5V supply and has
a nominal cutoff frequency of 5MHz optimized for
NTSC, PAL, and SDTV.
The MAX7445 has three modes of operation allowing
different video signals to be processed. The modes are
shown in Table 1. Mode 1 requires that channel A is a
video signal that includes a sync pulse. A sync separator uses this signal to extract the timing required to
clamp all four channels.
Modes 2 and 3 require that channel A and channel D
have a sync pulse to provide the required timing information. Channel A provides the required timing for channels
A, B, and C while channel D provides its own sync separator to extract the sync signal from an asynchronous
video signal.
Table 1. Operating Modes
MODE
MODE 1
CVBS/RGB
MODE 2
CVBS/Y/C/
CVBSASYNC
SELECT
GND
VCC
MODE 3
RGB/CVBSASYNC FLOATING
(G with sync)
CHANNEL
SIGNAL
A
CVBS
B
R
C
G
D
B
A
CVBS
B
Y
C
C
D
CVBSASYNC
A
G (with sync)
B
R
C
B
D
CVBSASYNC
Filter
Filter Response
The reconstruction filter consists of two 2nd-order SallenKey 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).
_______________________________________________________________________________________
5
MAX7445
Pin Description
MAX7445
4-Channel Video Reconstruction Filter
12dB Gain Setting
GAIN is biased internally to V CC / 2 with a resistordivider pair of 100kΩ resistors from VCC to GND such
that the internal impedance at the node is 50kΩ. No
additional connection is necessary since the input
offers a minimum noise-margin immunity of 1VP-P.
Table 2. High-Frequency Boost for Each
Mode
CHANNEL
HIGH-FREQUENCY BOOST (dB)
MODE 1
MODE 2
MODE 3
A
+1.2
+1.2
–
B
–
+1.2
–
C
–
+1.2
–
D
–
+1.2
+1.2
Output Clamp Level
When sync pulses are detected in either a CVBS or G
video signal, the DC restore loop is activated. The function of the loop is to set the DC level of the video signal
to a specified voltage. See Table 4 for clamp levels.
Table 3. Gain Setting Control
Applications Information
GAIN
BUFFER GAIN (dB)
GND
+6
VCC
+9.5
Floating
+12
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.
High-Frequency Boost
The high-frequency boost available on the CVBS, Y, and
C video channels increases image sharpness by compensating for signal degradation and roll-off in the video
encoder. Table 2 shows the channels that have the highfrequency boost option for the three operating modes.
The channels without high-frequency boost have a flat
response over the video bandwidth.
Output Buffers
Each output buffer can drive two 150Ω video loads with
a 2VP-P signal. The output buffer gain is selectable
between +6dB, +9.5dB, or +12dB by using GAIN (see
Table 3). The MAX7445 can drive an AC load or drive
the video load directly without using a large output
capacitor. The output buffers drive DC loads with an
output blanking level of less than 1V.
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 configuration, the voltage on the video cable is always less than
1V, complying with industry-standard video requirements 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.
Power-Supply Bypassing and Layout
The MAX7445 operates from a single +5V supply.
Bypass VCC to GND with a 0.1µF capacitor. Place all
external components as close to the device as possible.
Table 4. Output Clamp Level
CHANNEL
6
MODE 1: SELECT = GND
MODE 2: SELECT = VCC
MODE 3: SELECT = FLOATING
CLAMP LEVEL (V)
SYNC SOURCE
CLAMP LEVEL (V)
SYNC SOURCE
CLAMP LEVEL (V)
SYNC SOURCE
A
0.8
Channel A
0.8
Channel A
0.8
Channel A
B
1.4
Channel A
0.8
Channel A
1.4
Channel A
C
1.4
Channel A
1.6
Channel A
1.4
Channel A
D
1.4
Channel A
0.8
Channel D
0.8
Channel D
_______________________________________________________________________________________
4-Channel Video Reconstruction Filter
TOP VIEW
INA 1
14 OUTA
INB
2
13 OUTB
INC
3
12 OUTC
IND 4
MAX7445
11 OUTD
10 VCC
DISABLE 5
GND 6
9
SELECT
GAIN 7
8
GND
Exposed Pads
The TSSOP-EP package has an exposed pad on the
bottom of the package. This pad is electrically connected to GND and should be connected to the ground
plane for improved thermal conductivity. Do not route
signals under this package.
Chip Information
TRANSISTOR COUNT: 6300
PROCESS: BiCMOS
TSSOP
_______________________________________________________________________________________
7
MAX7445
Pin Configuration
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.)
TSSOP 4.4mm BODY.EPS
MAX7445
4-Channel Video Reconstruction Filter
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
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© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.