TLF6417

June 1989

54LS257ADM54LS257BDM74LS257B

54LS258ADM54LS258BDM74LS258B

TRI-STATE

Quad 2-Data SelectorsMultiplexers

General Description

These Schottky-clamped high-performance multiplexers

feature TRI-STATE outputs that can interface directly with

data lines of bus-organized systems With all but one of the

common outputs disabled (at a high impedance state) the

low impedance of the single enabled output will drive the

bus line to a high or low logic level To minimize the possibil-

ity that two outputs will attempt to take a common bus to

opposite logic levels the output enable circuitry is designed

such that the output disable times are shorter than the out-

put enable times

This TRI-STATE output feature means that n-bit (paralleled)

data selectors with up to 258 sources can be implemented

for data buses It also permits the use of standard TTL reg-

isters for data retention throughout the system

Features

Y

TRI-STATE versions LS157 and LS158 with same pin-

outs

Y

Schottky-clamped for significant improvement in A-C

performance

Y

Provides bus interface from multiple sources in high-

performance systems

Y

Average propagation delay from data input 12 ns

Y

Typical power dissipation

LS257B

50 mW

LS258B

35 mW

Y

Alternate

militaryaerospace

devices

(54LS257A

54LS258A) are available Contact a National Semicon-

ductor Sales OfficeDistributor for specifications

Connection Diagrams

Dual-In-Line Package

TLF6417 – 1

Order Number 54LS257ADMQB 54LS257AFMQB

54LS257ALMQB DM54LS257BJ DM54LS257BW

DM74LS257BM or DM74LS257BN

See NS Package Number E20A J16A

M16A N16E or W16A

Dual-In-Line Package

TLF6417 – 2

Order Number 54LS258ADMQB 54LS258AFMQB

54LS258ALMQB DM54LS258BJ DM54LS258BW

DM74LS258BM or DM74LS258BN

See NS Package Number E20A J16A

M16A N16E or W16A

Function Table

Inputs

Output Y

Output

Select

A

B

LS257

LS258

Control

HX

X

X

Z

Z

LL

L

X

L

H

LL

H

X

H

L

LH

X

L

L

H

LH

X

H

H

L

TRI-STATE

is a registered trademark of National Semiconductor Corporation

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A