Philips 74f251a DATASHEETS

Philips Semiconductors Product specification

74F251A8-input multiplexer (3-State)

FEA TURES

•High speed 8-to-1 multiplexing

•On chip decoding

•Multifunction capability

•Inverting and Non-Inverting outputs

•Both outputs are 3-State for further multiplexer expansion

DESCRIPTION

The 74F251A is a logic implementation of a single 8-position switch
with the switch position controlled by the state of three Select (S0,
S1, S2) inputs. True (Y) and complementary (Y
provided. The output enable (OE

) is active Low. When OE is High,
both outputs are in High impedance state, allowing multiple output
connections to a common bus without driving nor loading the bus
significantly . All but one device must be in High impedance state to
avoid high currents that would exceed the maximum ratings when
the outputs of the 3-State devices are tied together. When the output
of more than one device is tied together the user must ensure that
there is no overlap in the active Low portion of the output enable
voltages.

) outputs are both

PIN CONFIGURA TION

1

I3

2

I2
I1

3

I0

4

Y

5
6

Y

OE

TYPICAL

TYPE

PROPAGATION

DELA Y

74F251A 4.5ns 19mA

16

V

CC

15

I4

14

I5

13

I6

12

I7

11

S0

107

S1

98GND S2

TYPICAL

SUPPLY CURRENT

(TOTAL)

ORDERING INFORMATION

ORDER CODE

DESCRIPTION

16-pin plastic DIP N74F251AN SOT38-4

16-pin plastic SO N74F251AD SOT162-1

COMMERCIAL RANGE

= 5V ±10%,

V

CC

= 0°C to +70°C

T

amb

SF00778

PKG

DWG #

INPUT AND OUTPUT LOADING AND FAN-OUT TABLE

PINS DESCRIPTION 74F (U.L.) HIGH/LOW LOAD VALUE HIGH/LOW

I0–I7 Data inputs 1.0/1.0 20µA/0.6mA

S0–S2 Select inputs 1.0/1.0 20µA/0.6mA

OE Output Enable input (active Low) 1.0/1.0 20µA/0.6mA

Y, Y Data outputs 150/40 3mA/24mA

NOTE:

One (1.0) FAST unit load is defined as: 20µA in the High state and 0.6mA in the Low state.

LOGIC SYMBOL

11
10

9
7

V

= Pin 16

CC

GND = Pin 8

4 12131415

I0 I1 I2 I3 I4 I5 I6 I7
S0
S1

S2

OE

123

YY

65

SF00779

IEC/IEEE SYMBOL

7
11
10
9
4
3
2
1
15
14
13
12

EN

MUX

0

0

G

7

2

5

6

SF00780

1996 Jan 05 853–0358 16191

1

Philips Semiconductors Product specification

74F251A8-input multiplexer (3-State)

LOGIC DIAGRAM

I0 I1 I2 I3 I4 I5 I6 I7

4 3 2 1 15 14 13 12

OE

11

S0

10

S1

9

S2

7

V

= Pin 16

CC

GND = Pin 8

FUNCTION TABLE

INPUTS OUTPUTS

S2 S1 S0 OE Y Y

X X X H Z Z
L L L L I0 I0
L L H L I1 I1
L H L L I2 I2
L H H L I3 I3
H L L L I4 I4
H L H L I5 I5
H H L L I6 I6
H H H L I7 I7

NOTES:

H = High voltage level
L = Low voltage level
X = Don’t care
Z = High impedance “off” state

56

YY

SF00781

1996 Jan 05

2