MAX4028 データシートの表示（PDF） - Maxim Integrated

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MAX4028

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

Maxim Integrated 

MAX4028/MAX4029

Triple/Quad, 2:1 Video

Multiplexer-Amplifiers with Input Clamps

Pin Description (continued)

PIN

MAX4028 MAX4029

15

18

NAME

OUT1

Amplifier Output 1

FUNCTION

16

19

DISABLE

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

all outputs.

—

20

CLAMP/KEY_4

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

Drive CLAMP/KEY_4 low to key clamp OUT4.

IN1A

IN1B

IN2A

IN2B

CLAMP/KEY_2

IN3A

IN3B

CLAMP/KEY_3

A/B

IN4A

IN4B

CLAMP/KEY_4

KEYREF

CLAMP

CLAMP

CLAMP/

KEY

CLAMP

CLAMP/

KEY

CLAMP

CLAMP/

KEY

CLAMP

CLAMP/

KEY

CLAMP

VCC

1kΩ

1kΩ

1kΩ

1kΩ

1kΩ

1kΩ

CLAMP/

KEY

CLAMP

CLAMP/

KEY

CLAMP

CLAMP

VOLTAGE

1kΩ

1kΩ

MAX4029

GND

Figure 1. MAX4029 Functional Diagram

OUT1

OUT2

OUT3

OUT4

DISABLE

Detailed Description

The MAX4028/MAX4029 are 5V, triple/quad, 2:1

voltage-feedback 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/key-clamp inputs and fixed-

gain video output buffers make the MAX4028/MAX4029

ideal for video-source switching applications such as

entertainment systems, video projectors, and displays/

TVs. Both devices have 20ns channel switching times

and low ±10mVP-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 (2VP-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 accom-

modate 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 low-

est value, consistent with linear operation, and cannot be

adjusted. The key-clamp voltage is adjustable, to compen-

sate for variations in the voltage between component video

inputs such as Linear RGB, YPbPr, and Y-C, by varying

RKEYREF. The key-clamp voltage can be computed from:

VKey-Clamp = 0.40 + 2000/[(5000 x RKEYREF)/

(5000 + RKEYREF)]

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