Philips Semiconductors

Product specification

74ALS257/74ALS258

Data selector/multiplexer

74ALS257

Quad 2-input data selector, non-inverting (3-State)

74ALS258

Quad 2-input data selector, inverting (3-State)

2

1991 Feb 08

853–1130 01670

DESCRIPTION

The 74ALS257 is a quad 2-input multiplexer which selects 4 bits of

data from one of two sources under the control of a common select

input (S). The output enable input (OE) is active when Low. When

OE is High, all of the outputs (Yn) are forced to a High impedance

state (3-State) regardless of all other input conditions.

Moving data from two registers to a common output bus is a typical

use of the 74ALS257. The state of the select input determines the

particular register from which data comes.

The device is the logic implementation of 4-pole, 2-position switch

where the position of the switch is determined by the logic levels

supplied to the select input. The 74ALS258 is similar but has

inverting outputs (Yn).

TYPE

TYPICAL

PROPAGATION DELAY

TYPICAL

SUPPLY CURRENT

(TOTAL)

74ALS257

7.0ns

7mA

74ALS258

7.0ns

7mA

ORDERING INFORMATION

ORDER CODE

DESCRIPTION

COMMERCIAL RANGE

DRAWING

NUMBER

16-pin plastic DIP

74ALS257N, 74ALS258

SOT38-4

16-pin plastic SO

74ALS257D, 74ALS258D

SOT109-1

16-pin plastic SSOP

Type II

74ALS257DB, 74ALS258DB

SOT338-1

INPUT AND OUTPUT LOADING AND FAN-OUT TABLE

PINS

DESCRIPTION

74ALS (U.L.)

HIGH/LOW

LOAD VALUE

HIGH/LOW

Ina, Inb, Inc, Ind

Data inputs

1.0/1.0

20

µA/0.1mA

S

Select input

1.0/1.0

20

µA/0.1mA

OE

Enable input

1.0/1.0

20

µA/0.1mA

Ya – Yd, Ya – Yd

Data outputs

20/240

0.4mA/24mA

NOTE:

One (1.0) ALS unit load is defined as: 20

µA in the High state and 0.1mA in the Low state.

PIN CONFIGURATION – 74ALS257

16

15

14

13

12

11

10

7

6

5

4

3

2

1

Yb

Yd

I0c

I1c

I1d

OE

I0d

S

I0a

I1b

I1a

Ya

I0b

9

8

GND

Yc

SF00673

PIN CONFIGURATION – 74ALS258

16

15

14

13

12

11

10

7

6

5

4

3

2

1

Yb

Yd

I0c

I1c

I1d

OE

I0d

S

I0a

I1b

I1a

Ya

I0b

9

8

GND

Yc

SC00079