DM74LS257B datasheet, PDF - EEWORLD Datasheet

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DM74LS257B: Description3-STATE Quad 2-Data Selectors/Multiplexers; File Size56KB，5 Pages; ManufacturerFairchild; Websitehttp://www.fairchildsemi.com/

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DM74LS257B Overview

3-STATE Quad 2-Data Selectors/Multiplexers

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DM74LS257B 3-STATE Quad 2-Data Selectors/Multiplexers

June 1989

Revised November 1999

DM74LS257B

3-STATE Quad 2-Data Selectors/Multiplexers

General Description

These Schottky-clamped high-performance multiplexers

feature 3-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 pos-

sibility 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 output enable times.

This 3-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

3-STATE versions LS157 and LS158 with same pinouts

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: 50 mW

Ordering Code:

Order Number

DM74LS257BM

DM74LS257BN

Package Number

M16A

N16E

Package Description

16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow

16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.

Connection Diagram

Logic Diagram

Function Table

Inputs

Output

Control

HIGH Level

LOW Level

Output Y

LS257

Select

Don’t Care

High Impedance (off)

DS006417

www.fairchildsemi.com

DM74LS257B Related Products

	DM74LS257B	DM74LS257	74LS257	DM74LS257BM	DM74LS257BN
Description	3-STATE Quad 2-Data Selectors/Multiplexers	3-STATE Quad 2-Data Selectors/Multiplexers	3-STATE Quad 2-Data Selectors/Multiplexers	3-STATE Quad 2-Data Selectors/Multiplexers	3-STATE Quad 2-Data Selectors/Multiplexers

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