DM74LS257BMX - Fairchild Semiconductor

June 1989

Revised November 1999

DM74LS257B 3-STATE Quad 2-Data Selector s/Multiplexers

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 o utputs disabled (at a hi gh imp edance 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 sele ctors with up to 258 sou rces can be implem ented

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 dissi pati on: 50 mW

Ordering Code:

Devices also available in Tape and R eel. Speci fy by append ing the suffix let t er “X” to the orderin g c ode.

Connection Diagram

Function Table

H = HIGH Level X = Don’t Care

L = LOW Level Z = High Impedance (off)

Logic Diagram

Order Number Package Number Package Description

DM74LS257BM M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow

DM74LS257BN N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

Inputs Output Y

Output Select A B LS257

Control

HXXXZ

LLLXL

LLHXH

LHXLL

LHXHH

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DM74LS257B

Absolute Maximum Ratings(Note 1)

Note 1: The “Absolute Maximum Ratings” are thos e values bey ond which

the safety of the device cannot be guaranteed. the device should not be

operated at these limits. The parametric values defined in the Electrical

Characteristics tables are not guaranteed at the absolute maximum ratings.

The Recommended Operating Conditions table will define the conditions

for actu al device operation.

Recommended Operating Conditions

DC Electrical Characteristi cs

Note 2: All typical s are at VCC = 5V, TA = 25°C.

Note 3: Not more tha n one out put shoul d be shorte d at a t im e, and the duration sh ould not ex c eed one s ec ond.

Note 4: ICC is measu r ed with all out puts ope n and all possible in put s grounde d, w hile achi ev ing the stat ed output co ndition s .

Supply Voltage 7V

Input Voltag e 7V

Operating Free Air Temperature Range 0°C to +70°C

Storage Temperature Range −65°C to +150°C

Symbol Parameter Min Nom Max Units

VCC Supply Voltage 4.75 5 5.25 V

VIH HIGH Level Input Voltage 2 V

VIL LOW Level Input Voltage 0.8 V

IOH HIGH Level Output Current −2.6 mA

IOL LOW Level Output Current 24 mA

TAFree Air Operating Temperature 0 70 °C

Symbol Parameter Conditions Min Typ Max Units

(Note 2)

VIInput Clamp Voltage VCC = Min, II = −18 mA −1.5 V

VOH HIGH Level Output Voltage VIL = Max, VIH = Min 2.4 3.1 V

VOL LOW Level Output VIL = Max, VIH = Min 0.35 0.5 V

Voltage IOL = 12 mA, VCC = Min 0.25 0.4

IIInput Current @ Max VCC = Max, Select 0.2 mA

Input Voltage VI = 7V Other 0.1

IIH HIGH Level Input VCC = Max, Select 40 µA

Current VI = 2.7V Other 20

IIL LOW Level Input VCC = Max, Select −0.8 mA

Current VI = 0.4V Other −0.4

IOZH OFF-State Output Current with VCC = Max, VO = 2.7V 20 µA

HIGH Level Output Voltage Applied VIH = Min, VIL = Max

IOZL OFF-State Output Current with VCC = Max, VO = 0.4V −20 µA

LOW Level Output Voltage Applied VIH = Min, VIL = Max

IOS Short Circuit Output Current VCC = Max (Note 3) −20 −100 mA

ICCH Supply Current with Outputs HIGH VCC = Max (Note 4) 5.9 10 mA

ICCL Supply Current with Outputs LOW VCC = Max (Note 4) 9.2 16 mA

ICCZ Supply Current with Outputs Disabled VCC = Max (Note 4) 12 19 mA

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DM74LS257B

Switching Characteristics

VCC = 5V and TA = 25°C

Note 5: CL = 5 pF

Symbol Parameter

RL = 667Ω

UnitsFrom (Input ) CL = 45 pF CL = 150 pF

To (Output) Min Max Min Max

tPLH Propagation Delay Time Data to Output 18 27 ns

LOW-to-HIGH Level Output

tPHL Propagation Delay Time Data to Output 18 27 ns

HIGH-to-LOW Level Output

tPLH Propagation Delay Time Select to Output 28 35 ns

LOW-to-HIGH Level Output

tPHL Propagation Delay Time Select to Output 35 42 ns

HIGH-to-LOW Level Output

tPZH Output Enable Time Output Control to Y 15 27 ns

to HIGH Level Output

tPZL Output Enable Time Output Control to Y 28 38 ns

to LOW Level Output

tPHZ Output Disable Time from Output Control to Y 28 ns

HIGH Level Output (Note 5)

tPLZ Output Disable Time from Output Control to Y 25 ns

LOW Level Output (Note 5)

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DM74LS257B

Physical Dimensions inches (millimeters) unless otherwise noted

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

Package Number M16A

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

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DM74LS257B 3-STATE Quad 2-Data Selector s/Multiplexers

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

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

Package Number N16E

Fairchild does not assume an y responsibility for u se of any circuitry described, no circuit patent license s are implied and

Fairchild reserves the right at any time without notice to change said circuitry and specifications.

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FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

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body, or (b) support or sustain life, and (c) whose failure

to perform when properly used in accordance with

instruct ions fo r use pr ovi de d in the l abe ling, can be rea-

sonably expected to result in a significant injury to the

user.

2. A crit ical componen t in any com ponen t of a life s uppor t

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sonabl y e xpec ted to cause th e fa i lure of the l ife s upport

device or system, or to affect its safety or effectiveness.