510 -34 -2

9

BINARY ADDRESS

DECODER

VIDEO INPUTS

GX434 SWITCHES

V 0

V 1

V 2

V 3

75

75

75

75

0.1

1

2

6

5

4

3

7

9

10

11

12

13

14

8

1

2

6

5

4

3

7

9

10

11

12

13

14

8

1

2

6

5

4

3

7

9

10

11

12

13

14

8

1

2

6

5

4

3

7

9

10

11

12

13

14

8

V 4

V 5

V 6

V 7

75

75

75

75

V 8

V 9

V 10

V 11

75

75

75

75

V 12

V 13

V14

V15

75

75

75

75

0.1

0.1

0.1

0.1

0.1

0.1

0.1

-8V

-8V

+8V

-8V

+8V

+8V

A 0

A 1

330

2-10pF

IN 0

IN 1

IN 2

IN 3

+V

A 0

A 1

CS

OUT

-V

IN 0

IN 1

IN 2

IN 3

+V

A 0

A 1

CS

OUT

R

EXT

-V

IN 0

GND

IN 2

IN 3

+V

A 0

A 1

CS

OUT

-V

IN 0

IN 1

IN 2

IN 3

+V

A 0

A 1

CS

OUT

-V

A 2

ENABLE

A 3

4

5

6

7

-8V

+8V

GND

GND

GND

GND

GND

GND

GND

GND

GND

2

3

1

1

2

74HC139

GND

GND

IN 1

+5V

0.1

8

16

33K

1%

33K

1%

33K

1%

33K

1%

R

EXT

R

EXT

R

EXT

APPLICATIONS INFORMATION

The GX434 multiplexer is a very high performance,

wideband circuit requiring careful external circuit design.

Good power supply regulation and decoupling are

necessary to achieve optimum results. The circuit designer

must use proper lead dress, component placement and

PCB layout as in any high frequency circuit.

Functionally, the video switches are non-inverting, unity

gain bipolar switches with buffered inputs requiring DC

coupling and 75

Ω line terminating resistors when directly

driven from 75

Ω cable. The output must be buffered to

drive 75

Ω lines. This is usually accomplished with the

addition of an operational amplifier/ buffer which also

allows adjustments to be made to the gain, offset and

frequency response of the overall circuit.

A typical video routing application is shown in Figure 11.

Four ICs are used in a 16 x 1 multiplexer switching circuit.

An external address decoder is shown which generates

the 16 address and chip enable codes from a binary

number. The address inputs to each chip are active high

while the chip select inputs are active low. Depending on

the application and speed of the logic family used,

latches may be required for synchronization where timing

and delays are critical. Since the individual crosspoint

switching circuits are unidirectional bipolar elements, low

crosstalk and high isolation are inherent. The make-

before-break switching characteristics of the GX434

means virtually 'glitch' free switching.

+5V

0.1

-

+

3

2

4

7

-5V

0.1

75

500

6

250

300

100

Video

Out

All resistors in ohms, all capacitors in

microfarads unless otherwise stated.

Fig.11

16 x 1 Video Multiplexer Circuit

CLC 410 (comlinear)

DOCUMENT

IDENTIFICATION

PRODUCT PROPOSAL

This data has been compiled for market investigation purposes

only, and does not constitute an offer for sale.

ADVANCE INFORMATION NOTE

This product is in development phase and specifications are

subject to change without notice. Gennum reserves the right to

remove the product at any time. Listing the product does not

constitute an offer for sale.

PRELIMINARY DATA SHEET

The product is in a preproduction phase and specifications are

subject to change without notice.

DATA SHEET

The product is in production. Gennum reserves the right to make

changes at any time to improve reliability, function or design, in

order to provide the best product possible.

Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.

©Copyright August 1989 Gennum Corporation.

Revision date: January 1993.

All rights reserved.

Printed in Canada.