74F251A 8-Input Multiplexer with 3-STATE Outputs
April 1988
Revised September 2000
74F251A
8-Input Multiplexer with 3-STATE Outputs
General Description
The 74F251A is a high-speed 8-input digital multiplexer. It
provides, in one package, the ability to select one bit of
data from up to eight sources. It can be used as a universal
function generator to generate any logic function of four
variables. Both assertion and negation outputs are pro-
vided.
Features
s
Multifunctional capability
s
On-chip select logic decoding
s
Inverting and non-inverting 3-STATE outputs
Ordering Code:
Order Number
74F251ASC
74F251ASJ
74F251APC
Package Number
M16A
M16D
N16E
Package Description
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
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.
Logic Symbols
Connection Diagram
IEEE/IEC
© 2000 Fairchild Semiconductor Corporation
DS009504
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74F251A
Unit Loading/Fan Out
Pin Names
S
0
–S
2
OE
I
0
–I
7
Z
Z
Select Inputs
3-STATE Output Enable Input (Active LOW)
Multiplexer Inputs
3-STATE Multiplexer Output
Complementary 3-STATE Multiplexer Output
Description
U.L.
HIGH/LOW
1.0/1.0
1.0/1.0
1.0/1.0
150/40 (33.3)
150/40 (33.3)
Input I
IH
/I
IL
Output I
OH
/I
OL
20
µ
A/
−
0.6 mA
20
µ
A/
−
0.6 mA
20
µ
A/
−
0.6 mA
−
3 mA/24 mA (20 mA)
−
3 mA/24 mA (20 mA)
Functional Description
This device is a logical implementation of a single-pole, 8-
position switch with the switch position controlled by the
state of three Select inputs, S
0
, S
1
, S
2
. Both assertion and
negation outputs are provided. The Output Enable input
(OE) is active LOW. When it is activated, the logic function
provided at the output is:
Z
=
OE •(I
0
•S
0
•S
1
•S
2
+
I
1
•S
0
•S
1
•S
2
+
I
2
•S
0
•S
1
•S
2
+
I
3
•S
0
•S
1
•S
2
+
I
4
•S
0
•S
1
•S
2
+
I
5
•S
0
•S
1
•S
2
+
I
6
•S
0
•S
1
•S
2
+
I
7
•S
0
•S
1
•S
2
)
When the Output Enable is HIGH, both outputs are in the
high impedance (High Z) state. This feature allows multi-
plexer expansion by tying the outputs of up to 128 devices
together. When the outputs of the 3-STATE devices are
tied together, all but one device must be in the high imped-
ance state to avoid high currents that would exceed the
maximum ratings. The Output Enable signals should be
designed to ensure there is no overlap in the active LOW
portion of the enable voltages.
Truth Table
Inputs
OE
H
L
L
L
L
L
L
L
L
S
2
X
L
L
L
L
H
H
H
H
S
1
X
L
L
H
H
L
L
H
H
S
0
X
L
H
L
H
L
H
L
H
Outputs
Z
Z
I
0
I
1
I
2
I
3
I
4
I
5
I
6
I
7
Z
Z
I
0
I
1
I
2
I
3
I
4
I
5
I
6
I
7
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Immaterial
Z
=
High Impedance
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
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2
74F251A
Absolute Maximum Ratings
(Note 1)
Storage Temperature
Ambient Temperature under Bias
Junction Temperature under Bias
V
CC
Pin Potential to Ground Pin
Input Voltage (Note 2)
Input Current (Note 2)
Voltage Applied to Output
in HIGH State (with V
CC
=
0V)
Standard Output
3-STATE Output
Current Applied to Output
in LOW State (Max)
twice the rated I
OL
(mA)
−
65
°
C to
+
150
°
C
−
55
°
C to
+
125
°
C
−
55
°
C to
+
150
°
C
−
0.5V to
+
7.0V
−
0.5V to
+
7.0V
−
30 mA to
+
5.0 mA
Recommended Operating
Conditions
Free Air Ambient Temperature
Supply Voltage
0
°
C to
+
70
°
C
+
4.5V to
+
5.5V
−
0.5V to V
CC
−
0.5V to
+
5.5V
Note 1:
Absolute maximum ratings are values beyond which the device
may be damaged or have its useful life impaired. Functional operation
under these conditions is not implied.
Note 2:
Either voltage limit or current limit is sufficient to protect inputs.
DC Electrical Characteristics
Symbol
V
IH
V
IL
V
CD
V
OH
Parameter
Input HIGH Voltage
Input LOW Voltage
Input Clamp Diode Voltage
Output HIGH
Voltage
10% V
CC
10% V
CC
5% V
CC
5% V
CC
V
OL
I
IH
I
BVI
I
CEX
V
ID
I
OD
I
IL
I
OZH
I
OZL
I
OS
I
ZZ
I
CCL
I
CCZ
Output LOW Voltage
Input HIGH
Current
Input HIGH Current
Breakdown Test
Output HIGH
Leakage Current
Input Leakage
Test
Output Leakage
Circuit Current
Input LOW Current
Output Leakage Current
Output Leakage Current
Output Short-Circuit Current
Bus Drainage Test
Power Supply Current
Power Supply Current
15
16
−60
4.75
3.75
−0.6
50
−50
−150
500
22
24
10% V
CC
2.5
2.4
2.7
2.7
0.5
5.0
7.0
50
V
µA
µA
µA
V
µA
mA
µA
µA
mA
µA
mA
mA
Min
Max
Max
Max
0.0
0.0
Max
Max
Max
Max
0.0V
Max
Max
V
Min
Min
2.0
0.8
−1.2
Typ
Max
Units
V
V
V
Min
V
CC
Conditions
Recognized as a HIGH Signal
Recognized as a LOW Signal
I
IN
= −18
mA
I
OH
= −1
mA
I
OH
= −3
mA
I
OH
= −1
mA
I
OH
= −3
mA
I
OL
=
24 mA
V
IN
=
2.7V
V
IN
=
7.0V
V
OUT
=
V
CC
I
ID
=
1.9
µA
All Other Pins Grounded
V
IOD
=
150 mV
All Other Pins Grounded
V
IN
=
0.5V
V
OUT
=
2.7V
V
OUT
=
0.5V
V
OUT
=
0V
V
OUT
=
5.25V
V
O
=
LOW
V
O
=
HIGH Z
3
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74F251A
AC Electrical Characteristics
T
A
= +25°C
Symbol
Parameter
Min
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
t
PZH
t
PZL
t
PHZ
t
PLZ
t
PZH
t
PZL
t
PHZ
t
PLZ
Propagation Delay
S
n
to Z
Propagation Delay
S
n
to Z
Propagation Delay
I
n
to Z
Propagation Delay
I
n
to Z
Output Enable Time
OE to Z
Output Disable Time
OE to Z
Output Enable Time
OE to Z
Output Disable Time
OE to Z
3.5
3.2
4.5
4.0
3.0
1.5
3.5
3.5
2.5
2.5
2.5
1.5
3.5
3.5
2.0
1.5
V
CC
= +5.0V
C
L
=
50 pF
Typ
6.0
5.0
7.5
6.0
5.0
2.5
5.0
5.5
4.3
4.3
4.0
3.0
5.0
5.5
3.8
3.0
Max
9.0
7.5
10.5
8.5
6.5
4.0
7.0
7.0
6.0
6.0
5.5
4.5
7.0
7.5
5.5
4.5
T
A
= −55°C
to
+125°C
V
CC
=
5.0V
C
L
=
50 pF
Min
3.5
3.2
3.5
3.0
2.5
1.5
2.5
3.5
2.0
2.5
2.5
1.5
3.0
3.5
2.0
1.5
Max
11.5
8.0
14.0
10.5
8.0
6.0
9.0
9.0
7.0
7.5
6.0
5.0
8.5
9.0
5.5
5.5
T
A
=
0°C to
+70°C
V
CC
=
5.0V
C
L
=
50 pF
Min
3.5
3.2
4.5
4.0
3.0
1.5
2.5
3.5
2.5
2.5
2.5
1.5
3.0
3.5
2.0
1.5
Max
9.5
7.5
12.5
9.0
7.0
5.0
8.0
7.5
7.0
6.5
6.0
4.5
7.5
8.0
5.5
4.5
ns
ns
ns
ns
ns
ns
Units
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74F251A
Physical Dimensions
inches (millimeters) unless otherwise noted
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
Package Number M16A
5
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