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CY74FCT2257T

QUAD 2-INPUT MULTIPLEXER

WITH 3-STATE OUTPUTS

SCCS038B – SEPTEMBER 1994 – REVISED OCTOBER 2001

1

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

D

Function and Pinout Compatible With FCT

and F Logic

D

25-Ω Output Series Resistors to Reduce

Transmission-Line Reflection Noise

D

TTL Output Level Versions of Equivalent

FCT Functions

D

Edge-Rate Control Circuitry for

Significantly Improved Noise

Characteristics

D

I

off

Supports Partial-Power-Down Mode

Operation

D

Fully Compatible With TTL Input and

Output Logic Levels

D

ESD Protection Exceeds JESD 22

– 2000-V Human-Body Model (A114-A)

– 200-V Machine Model (A115-A)

– 1000-V Charged-Device Model (C101)

D

12-mA Output Sink Current

15-mA Output Source Current

D

3-State Outputs

description

The CY74FCT2257T has four identical two-input multiplexers that select four bits of data from two sources

under the control of a common data-select (S) input. The I

0

inputs are selected when S is low, and the I

1

inputs

are selected when S is high. Data appears at the output in noninverted form for the CY74FCT2257T. On-chip

termination resistors at the outputs reduce system noise caused by reflections. The CY74FCT2257T can

replace the FCT257T to reduce noise in an existing design.

The CY74FCT2257T is a logic implementation of a four-pole, two-position switch, in which the position of the

switch is determined by the logic levels supplied to S. Outputs are forced to the high-impedance off state when

the output-enable (OE

) input is high.

All but one device must be in the high-impedance state to prevent currents from exceeding the maximum ratings

if outputs are tied together. Design of the OE

signals must ensure that there is no overlap when outputs of 3-state

devices are tied together.

This device is fully specified for partial-power-down applications using I

off

. The I

off

circuitry disables the outputs,

preventing damaging current backflow through the device when it is powered down.

PIN DESCRIPTION

NAMEDESCRIPTION

IData inputs

SCommon data-select input

OEOutput-enable input (active low)

YData outputs

Copyright  2001, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

TexasInstruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

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16

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S

I

0a

I

1a

Y

a

I

0b

I

1b

Y

b

GND

V

CC

OE

I

0c

I

1c

Y

c

I

0d

I

1d

Y

d

Q OR SO PACKAGE

(TOP VIEW)

Produktspecifikationer