Datasheet > 74LS257

74LS257

更新时间： 2024-11-24 22:53:15

品牌	Logo	应用领域
美国国家半导体 - NSC		复用器
页数	文件大小	规格书
8页	166K
描述
TRI-STATE Quad 2-Data Selectors/Multiplexers

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数据手册

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74LS257 数据手册

June 1989

54LS257A/DM54LS257B/DM74LS257B,

54LS258A/DM54LS258B/DM74LS258B

TRI-STATE Quad 2-Data Selectors/Multiplexers

Features

General Description

TRI-STATE versions LS157 and LS158 with same pin-

outs

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.

Schottky-clamped for significant improvement in A-C

performance

Provides bus interface from multiple sources in high-

performance systems

Average propagation delay from data input 12 ns

Typical power dissipation

LS257B 50 mW

LS258B 35 mW

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.

Alternate military/aerospace devices (54LS257A/

54LS258A) are available. Contact a National Semicon-

ductor Sales Office/Distributor for specifications.

Connection Diagrams

Dual-In-Line Package

TL/F/6417–2

Order Number 54LS258ADMQB, 54LS258AFMQB,

54LS258ALMQB, DM54LS258BJ, DM54LS258BW,

DM74LS258BM or DM74LS258BN

TL/F/6417–1

Order Number 54LS257ADMQB, 54LS257AFMQB,

54LS257ALMQB, DM54LS257BJ, DM54LS257BW,

DM74LS257BM or DM74LS257BN

See NS Package Number E20A, J16A,

M16A, N16E or W16A

See NS Package Number E20A, J16A,

M16A, N16E or W16A

Function Table

Inputs

Output

Control

Output Y

Select

LS257 LS258

High Impedance (off)

Low Level, X Don’t Care,

High Level, L

TRI-STATEÉ is a registered trademark of National Semiconductor Corporation.

1995 National Semiconductor Corporation

TL/F/6417

RRD-B30M105/Printed in U. S. A.

12 3 4 5 6 7 8

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74LS257ADCQM	FAIRCHILD	获取价格	Multiplexer, 4-Func, 2 Line Input, TTL, CDIP16,
74LS257AFCQM	FAIRCHILD	获取价格	Multiplexer, 4-Func, 2 Line Input, TTL, CDFP16,
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74LS257APCQM	FAIRCHILD	获取价格	暂无描述
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74LS257ASC	FAIRCHILD	获取价格	Multiplexer, 4-Func, 2 Line Input, TTL, PDSO16
74LS257B	NXP	获取价格	LS SERIES, QUAD 2 LINE TO 1 LINE MULTIPLEXER, TRUE OUTPUT, PDIP16
74LS257DC	FAIRCHILD	获取价格	Multiplexer, 4-Func, 2 Line Input, TTL, CDIP16,
74LS257DCQM	FAIRCHILD	获取价格	Multiplexer, 4-Func, 2 Line Input, TTL, CDIP16,
74LS257FCQR	FAIRCHILD	获取价格	Multiplexer, 4-Func, 2 Line Input, TTL, CDFP16,