Rainbow Electronics MAX7445 User Manual

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.

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.

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 DVD Players

Game Consoles Digital VCRs

Desktop Video Editors

Features

♦ 4-Channel Filter and Buffer for CVBS, RGB, or Y/C

Video Signals

♦ 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

MAX7445

4-Channel Video Reconstruction Filter

________________________________________________________________ Maxim Integrated Products 1

Functional Diagram

Ordering Information

19-2948; Rev 0; 8/03

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.

*EP = Exposed pad.

Pin Configuration appears at end of data sheet.

PART TEMP RANGE PIN-PACKAGE

MAX7445EUD -40°C to +85°C 14 TSSOP-EP*

ENCODER

0.1µF
INA

D/A

0.1µF

D/A

0.1µF

D/A

SELECT

0.1µF

D/A

LOWPASS

FILTER

INB

LOWPASS

FILTER

INC

LOWPASS

FILTER

IND

LOWPASS

FILTER

V

SYNC

DETECTOR

SYNC

DETECTOR

GND

CC

75Ω

75Ω

75Ω

75Ω

75Ω

75Ω

75Ω

75Ω

MAX7445

DISABLE

OUTA

OUTB

OUTC

OUTD

GAIN

75Ω

*

75Ω

*

75Ω

*

75Ω

*

75Ω

*

75Ω

*

75Ω

*

75Ω

*

*OPTIONAL CAPACITORS

MAX7445

4-Channel Video Reconstruction Filter

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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, C

IN_

= 0.1µF,

GAIN = GND (+6dB) or V

CC

(+9.5dB), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +5V, TA= +25°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.

VCCto 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

Passband Response

Stopband Attenuation A

Differential Gain dG

Differential Phase dθ

Signal-to-Noise Ratio SNR

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

f = 100kHz to 5MHz,
relative to 100kHz

f ≥ 27MHz 39 43 dB

SB

5-step modulated
staircase

5-step modulated
staircase

Peak signal (2V
RMS noise,
f = 100Hz to 50MHz

P-P

Channel without
boost (see Table 2)

Channel with boost
(see Table 2)

Gain = +6dB,
+9.5dB

Gain = +12dB 0.25 0.90

Gain = +6dB,
+9.5dB

Gain = +12dB 0.15 0.60

) to

Gain = +6dB,
+9.5dB, +12dB

-0.75 +0.15 +0.75

+0.9 +1.2 +1.5

0.15 0.50

0.15 0.50

69 75 dB

dB

%

Degrees

Channel without

Group Delay Deviation

Line-Time Distortion H

Field-Time Distortion V

Clamp Settling Time t

Output DC Clamp Level

Low-Frequency Gain Accuracy A

Low-Frequency Gain Matching A

∆t

DIST

DIST

CLAMP

V ( M ATC H )

Deviation from 100kHz

g

to 4.1MHz

18µs, 100 IRE bar 0.3 %

130 lines, 18µs, 100 IRE bar 0.5 %

To ±1% 100 Lines

SELECT = GND

SELECT = V

SELECT = floating

f = 100kHz, relative to a gain of +6dB -3 +3 %

V

Low-frequency channel-to-channel matching,
f = 100kHz

CC

boost (see Table 2)

Channel with boost
(see Table 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

11 20

17 30

ns

V

4%

MAX7445

4-Channel Video Reconstruction Filter

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +5V ±5%, CL= 0 to 20pF, RL= 75Ω to GND for DC-coupled load, RL= 75Ω to VCC/ 2 for AC-coupled load, C

IN_

= 0.1µF,

GAIN = GND (+6dB) or V

CC

(+9.5dB), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +5V, TA= +25°C.)

Group Delay Matching

Channel-to-Channel Crosstalk X

Output Short-Circuit Current I

Input Leakage Current I

Input Dynamic Swing for Gain
of +6dB

SUPPLY

Supply Voltage Range V

Supply Current I

Power-Supply Rejection Ratio PSRR V

DISABLE

Output Impedance During
Disable

D i sab l e Log i c- Inp ut H i g h V ol tag eV

D i sab l e Log i c- Inp ut Low V ol tag eV

Disable Logic Input Current I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

t

g(MATCH)

Z

DISABLEVIL

TALK

SC

IN

CC

CC

DISABLE

IH

IL

Low-frequency channel-to-channel matching,
f = 100kHz

f = 100kHz to 3.58MHz 60 dB

OUT_ shorted to GND or V

SELECT = GND

SELECT = V

SELECT = floating

No load 100 140 mA

IN

At 5MHz 2 kΩ

2ns

CC

Channel A 1.2

Channels B, C, D 0.9

CC

= 100mV

= 0V (sink), VIH = VCC (source) ±10 µA

, f = 0 to 3.5MHz 40 dB

P-P

Channels A, B, D 1.2

Channel C 0.9

Channels A, D 1.2

Channels B, C 0.9

4.75 5.25 V

2.0 V

70 mA

10 µA

0.8 V

V

P-P

MAX7445

4-Channel Video Reconstruction Filter

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= +5V, V

GAIN

= 0V, TA = +25°C, unless otherwise noted.)

AMPLITUDE vs. FREQUENCY

MAX7445 toc01

FREQUENCY (MHz)

AMPLITUDE (dB)

10

-80

-60

-40

-20

0

1 100

NORMALIZED TO 0dB

PASSBAND AMPLITUDE vs. FREQUENCY

FREQUENCY (MHz)

AMPLITUDE (dB)

1

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

-2.0

0.1 10

MAX7445 toc02

NORMALIZED TO 0dB

FLAT PASSBAND RESPONSE

HIGH-FREQUENCY BOOST

PHASE RESPONSE vs. FREQUENCY

MAX7445 toc03

FREQUENCY (MHz)

PHASE (DEGREES)

1

-150

-100

-50

0

50

100

150

200

-200

0.1 10

GROUP DELAY vs. FREQUENCY

MAX7445 toc04

FREQUENCY (MHz)

GROUP DELAY (ns)

1

60

70

80

90

100

50

0.1 10

2T RESPONSE (1 IRE = 7.14mV)

MAX7445 toc05

200ns/div

250mV/

div

IN_

OUT_

250mV/

div

MODULATED 12.5T RESPONSE

(1 IRE = 7.14mV)

MAX7445 toc06

400ns/div

250mV/

div

IN_

OUT_

250mV/

div

SUPPLY CURRENT vs. TEMPERATURE

MAX7445 toc07

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

90

100

110

120

80

-40 85

INPUTS BIASED TO +2V
NO LOAD

DIFFERENTIAL GAIN

MAX7445 toc08

DIFFERENTIAL PHASE (DEGREES)

2nd1st 3rd 4th

5th

6th

2nd1st 3rd 4th

5th

6th

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

MAX7445 toc09

10µs/div

250mV/

div

IN_

OUT_

250mV/

div

MAX7445

4-Channel Video Reconstruction Filter

_______________________________________________________________________________________ 5

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.

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).

Pin Description

Table 1. Operating Modes

PIN NAME FUNCTION

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 DISABLE

6, 8 GND Ground

7 GAIN

9 SELECT

10 V

11 OUTD Channel D Video Output. This output can be either AC- or DC-coupled.

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.

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.

Gain-Control Input. Connect GAIN to GND for a gain of +6dB (+2V/V), to V
or leave unconnected for a gain of +12dB (+4V/V).

Mode Select Input. Connect to GND for CVBS/RGB processing, to V
processing, or leave floating for RGB/CVBS

+5V Supply Input

CC

(G with sync) processing.

ASYNC

MODE SELECT CHANNEL SIGNAL

MODE 1

CVBS/RGB

MODE 2

CVBS/Y/C/

CVBS

ASYNC

MODE 3

RGB/CVBS

(G with sync)

ASYNC

for a gain of +9.5dB (+3V/V),

CC

for CVBS/Y/C/CVBS

CC

GND

V

CC

FLOATING

ASYNC

A CVBS

BR

CG

DB

A CVBS

BY

CC

D CVBS

A G (with sync)

BR

CB

D CVBS

ASYNC

ASYNC

MAX7445

4-Channel Video Reconstruction Filter

6 _______________________________________________________________________________________

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 2V

P-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.

12dB Gain Setting

GAIN is biased internally to VCC/ 2 with a resistor­divider pair of 100kΩ resistors from VCCto 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 1V

P-P

.

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.

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.

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 VCCto GND with a 0.1µF capacitor. Place all
external components as close to the device as possible.

Table 2. High-Frequency Boost for Each
Mode

Table 3. Gain Setting Control

Table 4. Output Clamp Level

CHANNEL

A +1.2 +1.2 –

B – +1.2 –

C – +1.2 –

D – +1.2 +1.2

GAIN BUFFER GAIN (dB)

GND +6

V

CC

Floating +12

HIGH-FREQUENCY BOOST (dB)

MODE 1 MODE 2 MODE 3

+9.5

CHANNEL

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

MODE 1: SELECT = GND MODE 2: SELECT = V

CLAMP LEVEL (V) SYNC SOURCE CLAMP LEVEL (V) SYNC SOURCE CLAMP LEVEL (V) SYNC SOURCE

CC

MODE 3: SELECT = FLOATING

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

MAX7445

4-Channel Video Reconstruction Filter

_______________________________________________________________________________________ 7

Pin Configuration

TOP VIEW

INA

INB

INC

DISABLE

GND

1

2

3

4

5

6

7

14

OUTA

13

OUTB

12

OUTC

11

MAX7445

TSSOP

OUTDIND

V

10

CC

9

SELECT

GNDGAIN

8

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.

8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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