8-1

Semiconductor

January 1999

CA3256

25MHz, BiMOS Analog

Video Switch and Amplifier

CAUTION: These devices are sensitive to electrostatic discharge. Users should follow proper IC Handling Procedures.

Copyright

File Number

1769.5

Features

• 5 Multiplex Video Channels

- 1 Independent Channel

- 4 Channels with Enable

• 4 LED Channel Indicator Outputs

• Wideband Video Amplifier . . . . . . . . 25MHz Unity Gain

• Adjustable Video Amplifier Gain

• High Signal-Drive Capability

Applications

• Video Multiplex Switch

•75

Ω Video Amplifier/Line Driver

• Video Signal-Level Control

• Monitor Switching Control

• TV/CATV Audio/Video Switch

• Video Signal Adder/Fader Control

Description

The CA3256 BiMOS analog video switch has five channels

of CMOS multiplex switching for general-purpose video-

signal control. One of four CMOS channels may be selected

in parallel with channel 5. The CMOS switches are inputs to

the video amplifier but may be used in bilateral switching

between channels 1 to 4 and channel 5. The analog

switches of channels 1 to 4 are digitally controlled with logic

level conversion and binary decoding to select 1 of 4

channels. The enable function controls channels 1 to 4 but

does not affect channel 5. LED output drivers are selected

with the channel 1-to-4 switch selection to indicate the ON-

channel. Channel 5 may be used as a monitor output for

data or signal information on channels 1 to 4. The

transmission gate switches shown in the block diagram of

the CA3256 are configured in a “T” design to minimize

feedthrough. When the switch is off, the shunt or center of

the “T” is grounded.

transmission gate insertion loss. The amplifier output imped-

ance is typically 5

Ω in a complementary symmetry output.

The amplifier can directly drive a nominal 75

Ω coaxial cable

to provide line-to-line video switching. The gain of the ampli-

fier is programmable by different feedback resistor values

between pins 8 and 9. Compensation may also be used

between these pins for an optimally flat frequency response.

An internal regulated 5V bias reference with temperature

compensation permits stable direct-coupled output drive and

minimizes DC offset during signal switching.

Pinouts

Part Number Information

PART NUMBER

TEMP.

PACKAGE

PKG.

NO.

CA3256E

-40 to 85

18 Ld PDIP

E18.3

CA3256M

-40 to 85

20 Ld SOIC

M20.3

CA3256

(PDIP)

TOP VIEW

CA3256

(SOIC)

TOP VIEW

10

11

12

13

14

15

16

17

18

9

8

7

6

5

4

3

2

1

CONTROL B

CONTROL A

IN 1

IN/OUT 5

LED 1

LED 2

IN 2

LED 3

IN 3

LED 4

IN 4

GND

ENABLE

FEEDBACK

CONTROL C

AMP OUT

V-

V+

11

12

13

14

15

16

17

18

20

19

10

9

8

7

6

5

4

3

2

1

IN3

LED4

IN4

GND

V-

ENABLE

FEEDBACK

CONTROL C

AMP OUT

LED3

CONTROL B

CONTROL A

NC

IN1

IN2

V+

IN/OUT5

NC

LED1

LED2

[ /Title

(CA32

56)

/Sub-

ject

(25MH

z,

BiMO

S Ana-

log

Video

Switch

and

Ampli-

fier)

/Autho

r ()

/Key-

words

(Har-

ris

Semi-

con-

ductor,

4x1,

video

cross-

point

switch,

multi-

plexer

multi-

plexor,

cable

driver,

5x1,

moni

tor out-

put,

adjust-

able

gain,

OBSOLETE

PRODUCT

NO RECOMMENDED

REPLA

CEMENT

Call

Central

Applications

1-800-442-7747

or email:

centapp@harris.com