Datasheet DM74LS251N, DM74LS251MX, DM74LS251M, DM74LS251CW Datasheet (Fairchild Semiconductor)

© 2000 Fairchild Semiconductor Corporation DS006415 www.fairchildsemi.com

August 1986
Revised March 2000

DM74LS251 3-STATE 1-of-8 Line Data Selector/Multiplexer

DM74LS251
3-STATE 1-of-8 Line Data Selector/Multiplexer

General Description

These data selectors/multiplexers contain full on-chip
binary decoding to select one-o f-eight data sources, and
feature a strobe-controlled 3-STATE output. The strobe
must be at a low logic level to enable these devices. The 3­STATE outputs permit direct connection to a common bus.
When the strobe input is HIGH , both out put s are in a hig h­impedance state in which both the upper and lower transis­tors of each totem-pole output are OFF, and the output nei­ther drives nor loads the bus significantly. When the strobe
is LOW, the outputs are activa ted a nd op era te as standard
TTL totem-pole outputs.

To minimize the possibility that two outputs will attempt to
take a common bus to opposite logic levels, the output con­trol circuitry is designed so th at the ave rage ou tput disa ble
time is shorter than the average output enable time.

Features

■ 3-STATE version of DM74LS151

■ Interface directly with system bus

■ Perform parallel-to-serial conversion

■ Permit multiplexing from N-lines to one line

■ Complementary outputs provide true and inverted data

■ Maximum number of common outputs: 129

■ Typical propagation delay time (D to Y): 17 ns

■ Typical power dissipation: 35 mW

Ordering Code:

Devices also availab le in Tape and Reel. Specify by appending th e s uffix let t er “X” to the ordering code.

Connection Diagram Function Table

H = HIGH Logic Level
L = LOW Logic Level
X = Don't Care
Z = High Impedance (OF F )
D0, D1…D7 = The level of the respe ctiv e D input

Order Number Package Number Package Description

DM74LS251M M16A 16-Lead Small Outline Integrated Circuit (SOIC), JED EC MS-012, 0.150 Narrow
DM74LS251N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

Inputs Outputs

Select Strobe

YW

CBA S

XXX H Z Z
LLL L D0D0
LLH L D1D1
LHL L D2D2
LHH L D3D3
HLL L D4D4
HLH L D5D5
HHL L D6D6
HHH L D7D7

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DM74LS251

Logic Diagram

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DM74LS251

Absolute Maximum Ratings(Note 1)

Note 1: The “Absolute Maximum Ratings ” are those val ues beyond w hich

the safety of the device cannot be guaranteed. The device should not be
operated at thes e limits. The paramet ric values defined in the “Electrical
Characteristics” ta ble are not guaranteed at the absolute maxim um ratings.
The “Recommend ed O peratin g Cond itions” t able w ill defin e the condition s
for actual device operation.

Recommended Operating Conditions

Electrical Characteristics

over recommended operating free air temperature range (unless otherwise noted)

Note 2: All typicals are at VCC = 5V, TA = 25°C.
Note 3: Not more than one output should be shorted at a time, and the duration should not exceed one second.

Note 4: I

CC1

is measured with the outputs open, STROBE grounded, and all oth er inputs at 4.5V.

Note 5: I

CC2

is measured with the outputs open and all inp ut s at 4. 5V.

Supply Voltage 7V
Input Voltage 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

V

CC

Supply Voltage 4.75 5 5.25 V

V

IH

HIGH Level Input Voltage 2 V

V

IL

LOW Level Input Volta ge 0.8 V

I

OH

HIGH Level Output Current −2.6 mA

I

OL

LOW Level Output Current 24 mA

T

A

Free Air Operating Temperature 0 70 °C

Symbol Parameter Conditions Min

Typ

Max Units

(Note 2)

V

I

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

V

OH

HIGH Level VCC = Min, IOH = Max

2.4 3.1 V

Output Voltage VIL = Max, VIH = Min

V

OL

LOW Level VCC = Min, IOL = Max

0.35 0.5

Output Voltage VIL = Max, VIH = Min V

IOL = 12 mA, VCC = Min 0.25 0.4

I

I

Input Current @ Max Input Voltage VCC = Max, VI = 7V 0.1 mA

I

IH

HIGH Level Input Current VCC = Max, VI = 2.7V 20 µA

I

IL

LOW Level Input Current VCC = Max, VI = 0.4V −0.4 mA

I

OZH

Off-State Output Current with VCC = Max, VO = 2.7V

20 µA

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

I

OZL

Off-State Output Current with VCC = Max, VO = 0.4V

−20 µA

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

I

OS

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

I

CC1

Supply Current VCC = Max (Note 4) 6.1 10 mA

I

CC2

Supply Current VCC = Max (Note 5) 7.1 12 mA

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DM74LS251

Switching Characteristics

at VCC = 5V and TA = 25°C

Note 6: CL = 5 pF

From (Input) RL = 667Ω

Symbol Parameter

to (Output)

CL = 45 pF CL = 150 pF Units

Min Max Min Max

t

PLH

Propagation Delay Time A, B, C

45 53 ns

LOW-to-HIGH Level Output (4 Levels) to Y

t

PHL

Propagation Delay Time A, B, C

45 53 ns

HIGH-to-LOW Level Output (4 Levels) to Y

t

PLH

Propagation Delay Time A, B, C

33 38 ns

LOW-to-HIGH Level Output (3 Levels) to W

t

PHL

Propagation Delay Time A, B, C

33 42 ns

HIGH-to-LOW Level Output (3 Levels) to W

t

PLH

Propagation Delay Time

D to Y 28 35 ns

LOW-to-HIGH Level Output

t

PHL

Propagation Delay Time

D to Y 28 38 ns

HIGH-to-LOW Level Output

t

PLH

Propagation Delay Time

D to W 15 25 ns

LOW-to-HIGH Level Output

t

PHL

Propagation Delay Time

D to W 15 25 ns

HIGH-to-LOW Level Output

t

PZH

Output Enable Time to

Strobe to Y 45 60 ns

HIGH Level Output

t

PZL

Output Enable Time to

Strobe to Y 40 51 ns

LOW Level Output

t

PHZ

Output Disable Time from

Strobe to Y 45 ns

HIGH Level Output (Note 6)

t

PLZ

Output Disable Time from

Strobe to Y 25 ns

LOW Level Output (Note 6)

t

PZH

Output Enable Time to

Strobe to W 27 40 ns

HIGH Level Output

t

PZL

Output Enable Time to

Strobe to W 40 47 ns

LOW Level Output

t

PHZ

Output Disable Time from

Strobe to W 55 ns

HIGH Level Output (Note 6)

t

PLZ

Output Disable Time from

Strobe to W 25 ns

LOW Level Output (Note 6)

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DM74LS251

Physical Dimensions inches (millimeters) unless otherwise noted

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

Package Number M16A

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DM74LS251 3-STATE 1-of-8 Line Data Selector/Multiplexer

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 any responsibility for use of any circuitry described, no circuit pate nt licenses are implied and
Fairchild reserves the right at any time without notice to change said circuitry and specifications.

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to perform when properly used in accordance with
instructions for use provided in the labeling, can be rea­sonably expected to result in a significant inju ry to the
user.

2. A critical component in any com ponen t of a life su pport
device or system whose failu re to perform can be rea­sonably expected to ca use the fa i lure of the life su pp ort
device or system, or to affect its safety or effectiveness.

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