Rainbow Electronics MAX4029 User Manual

General Description

The MAX4028/MAX4029 are 5V, triple/quad, 2:1 voltage­feedback multiplexer-amplifiers with input clamps and a
fixed gain of +2V/V (6dB). Channel 1 (IN1A and IN1B)
inputs are clamped to the video sync tip of the input sig­nal, while the remaining inputs can be clamped to either
the video sync tip or the video sync of channel 1 (IN1_).
The latter is referred to as a key clamp and is pin selec­table. Selectable clamp/key-clamp inputs and fixed-gain
video output buffers make the MAX4028/MAX4029 ideal
for video-source switching applications such as automo­tive entertainment systems, video projectors, and dis­plays/TVs. Both devices have 20ns channel switching
times and low ±10mV

P-P

switching transients, making
them ideal for high-speed video switching applications
such as on-screen display (OSD) insertion.

The MAX4028/MAX4029 have a -3dB large-signal (2V

P-P

)
bandwidth of 130MHz, a -3dB small-signal bandwidth of
210MHz, and a 300V/µs slew rate. Low differential gain
and phase errors of 0.2% and 0.4°, respectively, make
these devices ideal for broadcast video applications.

The MAX4028/MAX4029 are specified over the -40°C to
+85°C extended temperature range and are offered in
16-pin and 20-pin TSSOP/SO packages.

Applications

In-Car Navigation/Entertainment

Blade Servers

Security Systems

Video Projectors

Displays and Digital Televisions

Broadcast and Graphics Video

Set-Top Boxes

Notebook Computers

Video Crosspoint Switching

Features

♦ Single +5V Operation
♦ Independently Selectable Sync-Tip or

Key-Clamp Inputs

♦ Adjustable Key-Clamp Voltage
♦ 130MHz Large-Signal -3dB Bandwidth
♦ 210MHz Small-Signal -3dB Bandwidth
♦ 300V/µs Slew Rate
♦ 20ns Switching Time
♦ Ultra-Low ±10mV

P-P

Switching Transient

♦ 0.2% Differential Gain/0.4° Phase Error
♦ Low-Power, High-Impedance Disable Mode

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

MAX4028
MAX4029

75Ω

75Ω

IN1A

V

CC

OUT1

CLAMP

A/B

+5V

C

IN

0.1µF

0.01µF

0.1µF

1kΩ

1kΩ

C

IN

0.1µF

IN1B

CLAMP

75Ω

75Ω

IN2A

OUT2

DISABLE

CLAMP/KEY_2

CLAMP

C

IN

0.1µF

R

KEYREF

6kΩ

1kΩ

1kΩ

C

IN

0.1µF

IN2B

KEYREF

CLAMP

KEY/CLAMP

CONTROL

75Ω CABLE

75Ω CABLE

75Ω CABLE

75Ω CABLE

75Ω

75Ω CABLE

75Ω

75Ω CABLE

Typical Operating Circuit

19-3240; Rev 0; 3/04

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.

Pin Configurations appear at end of data sheet.

Selector Guide

PART TEMP RANGE PIN-PACKAGE

MAX4028EUE -40°C to +85°C 16 TSSOP

MAX4028EWE -40°C to +85°C 16 Wide SO

MAX4029EUP -40°C to +85°C 20 TSSOP

MAX4029EWP -40°C to +85°C 20 Wide SO

PART

MAX4028 3 2V/V

MAX4029 4 2V/V

NO. OF 2:1

MUX-AMPS

GAIN

MAX4028/MAX4029

Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

DC ELECTRICAL CHARACTERISTICS

(VCC= +5V, GND = 0V, RL= 150Ω to GND, V

DISABLE

= +5V, R

KEYREF

= 6kΩ, CIN= 0.1µF to GND, TA= T

MIN

to T

MAX

, unless otherwise

noted. Typical values are at T

A

= +25°C.) (Note 2)

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.

Supply Voltage (VCCto GND) ..................................-0.3V to +6V

IN_A, IN_B, OUT_.......................................-0.3V to (V

CC

+ 0.3V)

DISABLE, A/B, KEYREF, CLAMP/KEY_......-0.3V to (V

CC

+ 0.3V)

Current Into IN_A, IN_B ...................................................±0.5mA

Short-Circuit Duration (V

OUT

to GND)........................Continuous

Short-Circuit Duration (V

OUT

to VCC) .............................(Note 1)

Continuous Power Dissipation (T

A

= +70°C)

16-Pin TSSOP (derate 9.4mW/°C above +70°C) .........755mW

16-Pin Wide SO (derate 9.5mW/°C above +70°C) ......762mW

20-Pin TSSOP (derate 11mW/°C above +70°C) ..........879mW

20-Pin Wide SO (derate 10mW/°C above +70°C) .......800mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Note 1: Do not short V

OUT

to VCC.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Supply Voltage Range V

Quiescent Supply Current I

CC

CC

Disable Supply Current V

Output Clamp Voltage V

Input Clamping Current I
Clamp Voltage Matching ∆V

Clamp Voltage Drift TC

Input Resistance R

Output Resistance R

Disable Output Resistance R

CLAMP

IN

CLAMP

VCLAMP

IN

OUT

OUT

Power-Supply Rejection Ratio PSRR 4.5V < VCC < 5.5V (Note 5) 48 58 dB

Voltage Gain A
Channel-to-Channel Gain Matching ∆A

Output-Voltage High V

Output-Voltage Low V

Output Current I

VCL

VCL

OH

OL

OUT

LOGIC INPUT CHARACTERISTICS (DISABLE , A/B, CLAMP/KEY_)

Logic-Low Threshold V

Logic-High Threshold V

Logic-Low Input Current I

Logic-High Input Current I

IL

IH

IL

IH

Guaranteed by PSRR 4.5 5.5 V

MAX4028, RL = ∞ 29 40

MAX4029, RL = ∞ 38 55

= 0V

DISABLE

Clamp (Note 3) 0.32 0.4 0.48

Key clamp (Note 4) 1.1

Input voltage = input clamp + 0.5V 5 18 µA

Measured at output 10 mV

Measured at output 80 µV/°C

V

= 0V 2 kΩ

DISABLE

VIL = 0V 6.6 25 µA

VIH = V

CC

MAX4028 9 15

MAX4029 11 20

7MΩ

0.7 Ω

1.9 2.0 2.1 V/V

±1 ±2 %

V

CLAMP

+ 2.4

V

CLAMP

30 mA

0.8 V

2.0 V

1.2 25 µA

mA

mA

V

V

V

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

_______________________________________________________________________________________ 3

AC ELECTRICAL CHARACTERISTICS

(VCC= +5V, GND = 0V, RL= 150Ω to GND, V

DISABLE

= +5V, R

KEYREF

= 6kΩ, CIN= 0.1µF, TA= T

MIN

to T

MAX

, unless otherwise noted.

Typical values are at T

A

= +25°C.)

Note 2: All devices are 100% production tested at T

A

= +25°C. Specifications over temperature are guaranteed by design.

Note 3: The clamp voltage at the input is V

CLAMP

(measured at the output) divided by gain + VBE.

Note 4: The key-clamp voltage is above the sync-tip clamp voltage by approximately 0.7V, and is adjusted by varying R

KEYREF

.

Note 5: Measured at f = 100Hz at thermal equilibrium.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Small-Signal -3dB Bandwidth BW

Large-Signal -3dB Bandwidth BW

Small-Signal 0.1dB Gain Flatness
Bandwidth

Large-Signal 0.1dB Gain Flatness
Bandwidth

SS

LS

BW

0.1dBSSVOUT

BW

0.1dBLSVOUT

Slew Rate SR V

Settling Time to 0.1% t

S

Power-Supply Rejection Ratio PSRR f = 100kHz 55 dB

Output Impedance Z

O

Differential Gain Error DG 5-step modulated staircase 0.2 %

Differential Phase Error DP 5-step modulated staircase 0.4 degrees

Group Delay D/dT f = 3.58MHz or 4.43MHz 1.0 ns

Peak Signal to RMS Noise SNR 100kHz to 30MHz 70 dB

Channel-to-Channel Crosstalk X

A/B Crosstalk X

Off-Isolation A

Droop D

TALK

TALKAB

ISO

R

SWITCHING CHARACTERISTICS

Channel Switching Time t

Enable Time t

Disable Time t

SW

ON

OFF

Switching Transient ±10 mV

V

= 100mV

OUT

V

= 2V

OUT

= 100mV

= 2V

= 2V

OUT

V

= 2V step 20 ns

OUT

P-P

P-P

P-P

P-P

P-P

210 MHz

130 MHz

30 MHz

30 MHz

300 V/µs

f = 100kHz 0.7 Ω

f = 100kHz 73 dB

f = 100kHz 91 dB

V

OUT_

= 2V

, f = 100kHz 108 dB

P-P

Guaranteed by input clamp current 2 %

20 ns

0.1 µs

0.1 µs

P-P

MAX4028/MAX4029

Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= +5V, GND = 0V, V

DISABLE

= +5V, RL= 150Ω to GND, CIN= 0.1µF, R

KEYREF

= 6.04kΩ ±1%, TA= +25°C, unless otherwise

noted.)

SMALL-SIGNAL BANDWIDTH

vs. FREQUENCY

MAX4028 toc01

FREQUENCY (Hz)

SMALL-SIGNAL BANDWIDTH (dB)

100M10M1M

-1

0

1

2

3

4

5

6

7

8

-2
100k 1G

V

OUT

= 100mV

P-P

SMALL-SIGNAL GAIN FLATNESS

vs. FREQUENCY

MAX4028 toc02

FREQUENCY (Hz)

GAIN FLATNESS (dB)

100M10M1M

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6.0

6.1

6.2

5.2
100k 1G

V

OUT

= 100mV

P-P

LARGE-SIGNAL BANDWIDTH

vs. FREQUENCY

MAX4028 toc03

FREQUENCY (Hz)

LARGE-SIGNAL BANDWIDTH (dB)

100M10M1M

-1

0

1

2

3

4

5

6

7

8

-2
100k 1G

V

OUT

= 2V

P-P

LARGE-SIGNAL GAIN FLATNESS

vs. FREQUENCY

MAX4028 toc04

FREQUENCY (Hz)

LARGE-SIGNAL GAIN FLATNESS (dB)

100M10M1M

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6.0

6.1

6.2

5.2
100k 1G

V

OUT

= 2V

P-P

DIFFERENTIAL GAIN AND PHASE

MAX4028 toc05

DIFFERENTIAL GAIN (%)

6th

5th4th3rd2nd

-0.1

-0.2

-0.3

0

0.1

0.2

0.3

1st

DIFFERENTIAL PHASE (deg)

6th

5th4th3rd2nd

-0.02

-0.04

-0.06

0

0.02

0.04

0.06

1st

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

MAX4028 toc06

FREQUENCY (Hz)

PSRR (dB)

100M10M1M100k10k

-60

-50

-40

-30

-20

-10

0

-70
1k 1G

OFF-ISOLATION

vs. FREQUENCY

MAX4028 toc07

FREQUENCY (Hz)

OFF-ISOLATION (dB)

100M10M1M

-120

-100

-80

-60

-40

-20

0

-140
100k 1G

ALL-HOSTILE CROSSTALK (CHANNEL TO

CHANNEL) vs. FREQUENCY

MAX4028 toc08

FREQUENCY (Hz)

CROSSTALK (dB)

100M10M100k 1M

-70

-60

-50

-40

-30

-20

-10

0

-80
10k 1G

ALL-HOSTILE CROSSTALK (A TO B ON ANY

CHANNEL) vs. FREQUENCY

MAX4028 toc09

FREQUENCY (Hz)

CROSSTALK (dB)

100M10M1M

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

-100
100k 1G

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(VCC= +5V, GND = 0V, V

DISABLE

= +5V, RL= 150Ω to GND, CIN= 0.1µF, R

KEYREF

= 6.04kΩ ±1%, TA= +25°C, unless otherwise

noted.)

OUTPUT IMPEDANCE

vs. FREQUENCY

100

10

1

OUTPUT IMPEDANCE (Ω)

0.1
10k 1G

FREQUENCY (Hz)

SMALL-SIGNAL TRANSIENT RESPONSE

V

IN

25mV/div

100M10M1M100k

MAX4028 toc13

INPUT-VOLTAGE NOISE DENSITY

vs. FREQUENCY

1000

MAX4028 toc10

100

10

INPUT-VOLTAGE NOISE DENSITY (nV/√Hz)

1

11M

FREQUENCY (Hz)

CHANNEL-SWITCHING TRANSIENT

1.6VDC

A/B

2.5V/div

LARGE-SIGNAL TRANSIENT RESPONSE

MAX4028 toc11

100k10k1k10010

500mV/div

V

OUT

1V/div

V

IN

10ns/div

CHANNEL-SWITCHING TIME

MAX4028 toc14

5VDC

2.5V/div

0VDC

(CHA = 1.5VDC, CHB = 1VDC)

A/B

MAX4028 toc12

1.6VDC

MAX4028 toc15

5VDC

0VDC

SIGNAL 2
50mV/div

ENABLE

2.5V/div

V

OUT

250mV/div

10ns/div

ENABLE RESPONSE TIME

= 0.5V)

(V

OUT

50ns/div

MAX4028 toc16

5VDC

0VDC

0.5VDC

0VDC

V

OUT

20mV/div

20ns/div

SMALL-SIGNAL BANDWIDTH

vs. FREQUENCY

11

10

9

8

7

6

5

4

3

SMALL-SIGNAL BANDWIDTH (dB)

2

1

100k 1G

C

= 15pF

LOAD

C

= 10pF

LOAD

C

LOAD

FREQUENCY (Hz)

= 5pF

V

OUT

500mV/div

20ns/div

OPTIMAL ISOLATION RESISTANCE

vs. CAPACITIVE LOAD

30

MAX4028 toc17

100M10M1M

25

20

15

10

5

OPTIMAL ISOLATION RESISTANCE (Ω)

0

0250

C

LOAD

20015010050

(pF)

MAX4028 toc18

MAX4028/MAX4029

Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps

6 _______________________________________________________________________________________

Pin Description

PIN

MAX4028

NAME FUNCTION

— 1 IN4A Amplifier Input 4A

1 2 IN3A Amplifier Input 3A

2 3 IN2A Amplifier Input 2A

3 4 IN1A Amplifier Input 1A

45 A/B

Channel-Select Input. Drive A/B high or leave floating to select channel A.
Drive A/B low to select channel B.

5 6 KEYREF

Key-Clamp Reference Output. Connect an external resistor from KEYREF to GND to
generate the key-clamp voltage.

6 7 IN1B Amplifier Input 1B

7 8 IN2B Amplifier Input 2B

8 9 IN3B Amplifier Input 3B

— 10 IN4B Amplifier Input 4B

— 11 OUT4 Amplifier Output 4

912

Output 3 Clamp or Key-Clamp Input. Drive CLAMP/KEY_3 high to clamp OUT3.
Drive CLAMP/KEY_3 low to key clamp OUT3.

10 13 GND Ground

11 14 OUT3 Amplifier Output 3

12 15

Output 2 Clamp or Key-Clamp Input. Drive CLAMP/KEY_2 high to clamp OUT2.
Drive CLAMP/KEY_2 low to key clamp OUT2.

13 16 OUT2 Amplifier Output 2

14 17 V

CC

Power-Supply Voltage. Bypass VCC to GND with 0.1µF and 0.01µF capacitors as
close to the pin as possible.

CLAMP VOLTAGE

vs. TEMPERATURE

MAX4028 toc19

TEMPERATURE (°C)

CLAMP VOLTAGE (V)

7550250-25

0.39

0.40

0.41

0.42

0.43

0.38

0.37

-50 100

Typical Operating Characteristics (continued)

(VCC= +5V, GND = 0V, V

DISABLE

= +5V, RL= 150Ω to GND, CIN= 0.1µF, R

KEYREF

= 6.04kΩ ±1%, TA= +25°C, unless otherwise

noted.)

KEY-CLAMP REFERENCE VOLTAGE

vs. R

KEYREF

MAX4028 toc20

R

KEYREF

(kΩ)

KEY-CLAMP REFERENCE VOLTAGE (V)

119753

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0

113

MAX4029

CLAMP/KEY_3

CLAMP/KEY_2

Detailed Description

The MAX4028/MAX4029 are 5V, triple/quad, 2:1 voltage­feedback multiplexer-amplifiers with input clamps and a
fixed gain of +2V/V (6dB). Channel 1 (IN1A and IN1B)
inputs are clamped to the video sync tip of the input
IN1_ channel, while the remaining inputs can be
clamped to either the video sync tip of the respective
input channel (IN_A and IN_B) or the video sync of
channel 1 (IN1_). The latter is referred to as a key
clamp and is pin selectable. Selectable clamp/key­clamp inputs and fixed-gain video output buffers make
the MAX4028/MAX4029 ideal for video-source switching
applications such as automotive entertainment systems,
video projectors, and displays/TVs. Both devices have
20ns channel switching times and low ±10mV

P-P

switch­ing transients, making them ideal for both high-speed
video switching applications such as OSD insertion.

The MAX4028/MAX4029 have a -3dB large-signal (2V

P-P

)
bandwidth of 130MHz, a -3dB small-signal bandwidth of
210MHz, and a 300V/µs slew rate. Low differential gain
and phase errors of 0.2% and 0.4°, respectively, make
these devices ideal for broadcast video applications.

Sync Tip and Key Clamps

The MAX4028/MAX4029 have AC-coupled inputs, with
either a sync tip or key clamp to provide bias for the
video signal. Channel 1 of the MAX4028/MAX4029
always has a sync tip clamp at the input, while the
remaining channels are selectable as either sync tip or
key clamps to accommodate the various video wave­forms (see the Clamp/Key-Clamp Settings for Video
Formats section). The value of the sync-tip clamp voltage
is set internally for the lowest value, consistent with linear
operation, and cannot be adjusted. The key-clamp volt­age is adjustable, to compensate for variations in the
voltage between component video inputs such as Linear
RGB, YPbPr, and Y-C, by varying R

KEYREF

. The key-

clamp voltage can be computed from:

V

Key-Clamp

= 0.40 + 2000/[(5000 x R

KEYREF

) /

(5000 + R

KEYREF

)]

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

_______________________________________________________________________________________ 7

Pin Description (continued)

PIN

NAME FUNCTION

15 18 OUT1 Amplifier Output 1

16 19 DISABLE

Disable Input. Pull DISABLE high for normal operation. Drive DISABLE low to disable
all outputs.

— 20

Output 4 Clamp or Key-Clamp Input. Drive CLAMP/KEY_4 high to clamp OUT4.
Drive CLAMP/KEY_4 low to key clamp OUT4.

Figure 1. MAX4029 Functional Diagram

MAX4028 MAX4029

CLAMP/KEY_4

IN1A

CLAMP

IN1B

CLAMP

1kΩ

IN2A

CLAMP/

KEY

CLAMP

IN2B

CLAMP/

KEY

CLAMP/KEY_2

IN3A

IN3B

CLAMP/KEY_3

A/B

IN4A

IN4B

CLAMP/KEY_4

KEYREF

CLAMP

CLAMP/

KEY

CLAMP

CLAMP/

KEY

CLAMP

CLAMP/

KEY

CLAMP

CLAMP/

KEY

CLAMP

CLAMP

VOLTAGE

1kΩ

1kΩ

1kΩ

GND

V

CC

1kΩ

1kΩ

1kΩ

1kΩ

MAX4029

OUT1

OUT2

OUT3

OUT4

DISABLE

MAX4028/MAX4029

Therefore, a 6kΩ resistor will produce a 1.13V key­clamp voltage as shown in Figure 2. The clamp voltage

(V

CLAMP

) is measured at the output; the voltage at the

input is V

CLAMP

(sync tip or key clamp) divided by the

gain (+2V/V) + V

BE

.

In order for these clamps (sync tip or key) to work proper­ly, the input must be coupled with a 0.1µF capacitor (typ)
with low leakage (<1µA to 2µA, max). Without proper cou­pling, the clamp voltage will change during the horizontal
line time causing the “black level” to vary, changing the
image brightness from left to right on the display. In addi-

tion to the capacitor, a low resistance (≤75Ω) is required
on the source side to return the capacitor to ground. The
clamps used here are active devices with the coupling
capacitor serving two functions; first, as a charge reser­voir to maintain the clamp voltage, and second, as the
compensation capacitor for the clamp itself. If an input is
not used, it must be terminated to avoid causing oscilla­tions that could couple with another input.

In general, a sync-tip clamp is used for composite video
(Cvbs), gamma corrected primaries (R’G’B’), and the
luma signal (Y) in S-video. A key clamp is preferred for
component color difference signals (Pb and Pr), linear
primaries (RGB in PCs), and chroma (C) in S-video. The
rule is to sync tip clamp a signal if sync is present and
key clamp all others. Several examples are given in the
Clamp/Key-Clamp Settings for Video Formats section.

Clamp/Key-Clamp Settings for Video Formats

Tables 1 and 2 provide the clamp settings on the
MAX4028/MAX4029 to interface with various video formats.

Low-Power, High-Impedance Disable Mode

All parts feature a low-power, high-impedance disable
mode that is activated by driving the DISABLE input
low. Placing the amplifier in disable mode reduces the
quiescent supply current and places the output imped­ance at 2kΩ typically. Multiple devices can be paral­leled to construct larger switch matrices by connecting
the outputs of several devices together and disabling
all but one of the paralleled amplifiers’ outputs.

Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps

8 _______________________________________________________________________________________

Figure 2. Key-Clamp Reference Voltage vs. R

KEYREF

Table 1. MAX4028 Clamp Settings for Video Formats

R, G, B have sync on all.

Gs, B, R have sync only on Green.

KEY-CLAMP REFERENCE VOLTAGE

vs. R

R

KEYREF

KEYREF

MAX4028 fig02

119753

(kΩ)

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

KEY-CLAMP REFERENCE VOLTAGE (V)

0.2

0

113

INPUT FORMAT CLAMP/KEY

1 Cvbs1 Clamp

2 Cvbs2 Clamp

3 Cvbs3 Clamp

INPUT FORMAT CLAMP/KEY

1G’ Clamp

2B’ Clamp

3R’ Clamp

INPUT FORMAT CLAMP/KEY

1 Gs Clamp

2 B Key

3 R Key

INPUT FORMAT CLAMP/KEY

1 Y Clamp

2 C Key

3 Cvbs Clamp

INPUT FORMAT CLAMP/KEY

1 Y Clamp

2 Pb Key

3 Pr Key

The MAX4028/MAX4029 have a fixed gain of +2V/V that
is internally set with two 1kΩ thin-film resistors. The
impedance of the internal feedback resistors must be
taken into account when operating multiple MAX4028/
MAX4029s in large multiplexer applications.

Applications Information

Video Line Driver

The MAX4028/MAX4029 are well suited to drive coaxial
transmission lines when the cable is terminated at both
ends, as shown in Figure 3, where the fixed gain of

+2V/V compensates for the loss in the resistors, RT.

Driving Capacitive Loads

A correctly terminated transmission line is purely resis­tive and presents no capacitive load to the amplifier.
Reactive loads decrease phase margin and may pro­duce excessive ringing and oscillation.

Another concern when driving capacitive loads is the
amplifier’s output impedance, which appears inductive
at high frequencies. This inductance forms an L-C reso-

nant circuit with the capacitive load, which causes
peaking in the frequency response and degrades the
amplifier’s phase margin.

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

_______________________________________________________________________________________ 9

Table 2. MAX4029 Clamp Settings for Video Formats

Gs, B, R have sync only on Green.

R, G, B have sync on none.

R, G, B have sync on all.

Figure 3. Video Line Driver

INPUT FORMAT CLAMP/KEY

1 Cvbs1 Clamp

2 Cvbs2 Clamp

3 Cvbs3 Clamp

4 Cvbs4 Clamp

INPUT FORMAT CLAMP/KEY

1 H-Sync Clamp

2 G Key

3 B Key

4 R Key

INPUT FORMAT CLAMP/KEY

1 Y Clamp

2 C Key

3 Cvbs Clamp

4 Cvbs Clamp

75Ω CABLE

75Ω

75Ω CABLE

75Ω

R

R

R

KEYREF

INPUT FORMAT CLAMP/KEY

1 Gs Clamp

2 R Key

3 B Key

4 Cvbs Clamp

INPUT FORMAT CLAMP/KEY

1 Y Clamp

2 Pr Key

3 Pb Key

4 Cvbs Clamp

INPUT FORMAT CLAMP/KEY

1 Cvbs Clamp

2G’ Clamp

3B’ Clamp

4R’ Clamp

A/B DISABLE

0.1µF

IN_A

T

0.1µF

IN_B

T

CLAMP

MAX4028
MAX4029

OUT_

R

75Ω

T

75Ω CABLE

R
75Ω

T

MAX4028/MAX4029

Although the MAX4028/MAX4029 are optimized for AC
performance and are not designed to drive highly
capacitive loads, they are capable of driving up to
15pF without oscillations. However, some peaking may
occur in the frequency domain (Figure 4). To drive larg-

er capacitive loads or to reduce ringing, add an isola­tion resistor between the amplifier’s output and the load
(Figure 5). The value of R

ISO

depends on the circuit’s

gain (+2V/V) and the capacitive load (Figure 6). Also
note that the isolation resistor forms a divider that
decreases the voltage delivered to the load.

Layout and Power-Supply Bypassing

The MAX4028/MAX4029 have high bandwidths and
consequently require careful board layout, including
the possible use of constant-impedance microstrip or
stripline techniques.

To realize the full AC performance of these high-speed
amplifiers, pay careful attention to power-supply
bypassing and board layout. The PC board should
have at least two layers: a signal and power layer on
one side, and a large, low-impedance ground plane on
the other side. The ground plane should be as free of
voids as possible. Whether or not a constant-imped­ance board is used, it is best to observe the following
guidelines when designing the board:

1) Do not use wire-wrapped boards or breadboards.

2) Do not use IC sockets; they increase parasitic

capacitance and inductance.

3) Keep signal lines as short and straight as possible.

Do not make 90° turns; round all corners.

4) Observe high-frequency bypassing techniques to

maintain the amplifier’s accuracy and stability.

5) Use surface-mount components. They generally

have shorter bodies and lower parasitic reactance,
yielding better high-frequency performance than
through-hole components.

Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps

10 ______________________________________________________________________________________

Figure 4. Small-Signal Gain vs. Frequency with Capacitive
Load and No Isolation Resistor

Figure 5. Using an Isolation Resistor (R

ISO

) for a High-

Capacitive Load

Figure 6. Optimal Isolation Resistance vs. Capacitive Load

SMALL-SIGNAL BANDWIDTH

vs. FREQUENCY

11

10

9

8

7

6

5

4

3

SMALL-SIGNAL BANDWIDTH (dB)

2

1

100k 1G

C

= 15pF

LOAD

C

= 10pF

LOAD

C

LOAD

FREQUENCY (Hz)

MAX4028 fig04

= 5pF

100M10M1M

A/B DISABLE

75Ω CABLE

75Ω CABLE

R

75Ω

75Ω

KEYREF

0.1µF

IN_A

R

T

0.1µF

IN_B

R

T

CLAMP

MAX4028
MAX4029

OUT_

R

ISO

OPTIMAL ISOLATION RESISTANCE

vs. CAPACITIVE LOAD

30

25

20

15

10

5

OPTIMAL ISOLATION RESISTANCE (Ω)

0

0 250

C

(pF)

LOAD

20015010050

MAX4028 fig06

C

R

L

L

The bypass capacitors should include a 0.1µF, ceramic
surface-mount capacitor between VCCand the ground
plane, located as close to the package as possible.
Optionally, place a 10µF capacitor at the power supply’s
point-of-entry to the PC board to ensure the integrity of
incoming supplies. The power-supply traces should lead

directly from the capacitor to the VCCpin. To minimize
parasitic inductance, keep PC traces short and use sur­face-mount components.

If input termination resistors and output back-termination
resistors are used, they should be surface-mount types,
and should be placed as close to the IC pins as possible.

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

______________________________________________________________________________________ 11

Pin Configurations

Chip Information

TRANSISTOR COUNT: 1032

PROCESS: Bipolar

TOP VIEW

IN3A

IN2A

IN1A

A/B

KEYREF

IN1B

IN2B

IN3B

1

2

3

4

5

6

7

8

MAX4028

TSSOP/SO

16

DISABLE

15

OUT1

14

V

CC

13

OUT2

12

CLAMP/KEY_2

OUT3

11

10

GND

9

CLAMP/KEY_3

IN4A

IN3A

IN2A

IN1A

A/B

KEYREF

IN1B

IN3B

1

2

3

4

5

6

7

8

9

10

MAX4029

TSSOP/SO

20

CLAMP/KEY_4

19

DISABLE

18

OUT1

17

V

CC

16

OUT2

15

CLAMP/KEY_2

14

OUT3

13

GNDIN2B

12

CLAMP/KEY_3

11

OUT4IN4B

MAX4028/MAX4029

Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps

12 ______________________________________________________________________________________

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

.)

TSSOP4.40mm.EPS

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

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.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13

© 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

Package Information (continued)

(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

.)

A1

MAX

0.104

0.019

0.299

0.050

MAX

0.5120.496D

MILLIMETERS

MAX

MIN

2.65

2.35

0.30

0.10

0.49

0.35

0.23

0.32

7.40 7.60

0.40 1.27

MILLIMETERS

MAX

MIN

12.60 13.00

N MS013

20

AC

INCHES

MIN

DIM

0.093A

0.012

0.004

A1

0.014

B
C

H

E

A

C

L

e 0.050 1.27
E
H 0.4190.394 10.00 10.65

VARIATIONS:

D
D

D 0.6140.598 15.20 2415.60 AD
D 0.7130.697 17.70 2818.10 AE

0-8

0.013

0.009

0.291

0.016L

INCHES

MINDIM

0.398 0.413 AA10.5010.10 16

0.447 0.463 AB11.7511.35 18

SIDE VIEW

N

1

TOP VIEW

D

e

FRONT VIEW

B

SOICW.EPS

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, .300" SOIC

REV.DOCUMENT CONTROL NO.APPROVAL

21-0042

1

B

1