74AC251 • 74ACT251 8-Input Multiplexer with 3-STATE Output
November 1988
Revised November 1999
74AC251 • 74ACT251
8-Input Multiplexer with 3-STATE Output
General Description
The AC/ACT251 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 universal
function generator to generate any logic function of four
variables. Both true and complementary outputs are pro-
vided.
Features
s
I
CC
reduced by 50%
s
Multifunctional capability
s
On-chip select logic decoding
s
Inverting and noninverting 3-STATE outputs
s
Outputs source/sink 24 mA
s
ACT251 has TTL-compatible inputs
Ordering Code:
Order Number
74AC251SC
74AC251SJ
74AC251MTC
74AC251PC
74ACT251SC
74ACT251MTC
74ACT251PC
Package Number
M16A
M16D
MTC16
N16E
M16A
MTC16
N16E
Package Description
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150” Narrow Body
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150” Narrow Body
16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering code.
Logic Symbols
Connection Diagram
IEEE/IEC
Pin Descriptions
Pin Names
S
0
–S
2
OE
I
0
–I
7
Z
Z
Select Inputs
3-STATE Output Enable Input
Multiplexer Inputs
3-STATE Multiplexer Output
Complementary 3-STATE Multiplexer Output
Description
FACT is a trademark of Fairchild Semiconductor Corporation.
© 1999 Fairchild Semiconductor Corporation
DS009945
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74AC251 • 74ACT251
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 true and com-
plementary 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
Z
Z
I
0
I
1
I
2
I
3
I
4
I
5
I
6
I
7
Outputs
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
74AC251 • 74ACT251
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
CC
)
DC Input Diode Current (I
IK
)
V
I
= −0.5V
V
I
=
V
CC
+
0.5V
DC Input Voltage (V
I
)
DC Output Diode Current (I
OK
)
V
O
= −0.5V
V
O
=
V
CC
+
0.5V
DC Output Voltage (V
O
)
DC Output Source
or Sink Current (I
O
)
DC V
CC
or Ground Current
per Output Pin (I
CC
or I
GND
)
Storage Temperature (T
STG
)
Junction Temperature (T
J
)
PDIP
140°C
±50
mA
−65°C
to
+150°C
±50
mA
−20
mA
+20
mA
−0.5V
to V
CC
+
0.5V
−20
mA
+20
mA
−0.5V
to V
CC
+
0.5V
−0.5V
to
+7.0V
Recommended Operating
Conditions
Supply Voltage (V
CC
)
AC
ACT
Input Voltage (V
I
)
Output Voltage (V
O
)
Operating Temperature (T
A
)
Minimum Input Edge Rate (∆V/∆t)
AC Devices
V
IN
from 30% to 70% of V
CC
V
CC
@ 3.3V, 4.5V, 5.5V
Minimum Input Edge Rate (∆V/∆t)
ACT Devices
V
IN
from 0.8V to 2.0V
V
CC
@ 4.5V, 5.5V
125 mV/ns
Note 1:
Absolute maximum ratings are those values beyond which damage
to the device may occur. The databook specifications should be met, with-
out exception, to ensure that the system design is reliable over its power
supply, temperature, and output/input loading variables. Fairchild does not
recommend operation of FACT circuits outside databook specifications.
2.0V to 6.0V
4.5V to 5.5V
0V to V
CC
0V to V
CC
−40°C
to
+85°C
125 mV/ns
DC Electrical Characteristics for AC
Symbol
V
IH
Parameter
Minimum HIGH Level
Input Voltage
V
IL
Maximum LOW Level
Input Voltage
V
OH
Minimum HIGH Level
Output Voltage
V
CC
(V)
3.0
4.5
5.5
3.0
4.5
5.5
3.0
4.5
5.5
3.0
4.5
5.5
V
OL
Maximum LOW Level
Output Voltage
3.0
4.5
5.5
3.0
4.5
5.5
I
IN
(Note 4)
I
OZ
Maximum Input Leakage Current
Maximum 3-STATE
Current
I
OLD
I
OHD
Minimum Dynamic
Output Current (Note 3)
5.5
5.5
5.5
5.5
4.0
±0.25
±2.5
75
−75
40.0
µA
mA
mA
µA
5.5
0.002
0.001
0.001
T
A
= +25°C
Typ
1.5
2.25
2.75
1.5
2.25
2.75
2.99
4.49
5.49
2.1
3.15
3.85
0.9
1.35
1.65
2.9
4.4
5.4
2.56
3.86
4.86
0.1
0.1
0.1
0.36
0.36
0.36
±0.1
T
A
= −40°C
to
+85°C
Guaranteed Limits
2.1
3.15
3.85
0.9
1.35
1.65
2.9
4.4
5.4
V
IN
=
V
IL
or V
IH
2.46
3.76
4.76
0.1
0.1
0.1
V
IN
=
V
IL
or V
IH
0.44
0.44
0.44
±1.0
µA
V
I
OL
= 12 mA
I
OL
= 24 mA
I
OL
= 24 mA (Note 2)
V
I
=
V
CC
, GND
V
I
(OE)
=
V
IL
, V
IH
V
I
=
V
CC
, V
GND
V
O
=
V
CC
, GND
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
or GND
V
I
OUT
=
50
µA
V
I
OH
=
−12
mA
I
OH
=
−24
mA
I
OH
=
−24
mA (Note 2)
V
I
OUT
= −50 µA
V
V
OUT
=
0.1V
or V
CC
−
0.1V
V
Units
Conditions
V
OUT
=
0.1V
or V
CC
−
0.1V
I
CC
(Note 4) Maximum Quiescent Supply Curent
Note 2:
All outputs loaded; thresholds on input associated with output under test.
Note 3:
Maximum test duration 2.0 ms, one output loaded at a time.
Note 4:
I
IN
and I
CC
@ 3.0V are guaranteed to be less than or equal to the respective limit @ 5.5V V
CC
.
3
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74AC251 • 74ACT251
DC Electrical Characteristics for ACT
Symbol
V
IH
V
IL
V
OH
Parameter
Minimum HIGH Level
Input Voltage
Maximum LOW Level
Input Voltage
Minimum HIGH Level
Output Voltage
V
CC
(V)
4.5
5.5
4.5
5.5
4.5
5.5
4.5
5.5
V
OL
Maximum LOW Level
Output Voltage
4.5
5.5
4.5
5.5
I
IN
I
OZ
I
CCT
I
OLD
I
OHD
I
CC
Maximum Input
Leakage Current
Maximum 3-STATE
Current
Maximum
I
CC
/Input
Minimum Dynamic
Output Current (Note 6)
Maximum Quiescent
Supply Current
5.5
5.5
5.5
5.5
5.5
5.5
4.0
0.6
0.001
0.001
T
A
= +25°C
Typ
1.5
1.5
1.5
1.5
4.49
5.49
2.0
2.0
0.8
0.8
4.4
5.4
3.86
4.86
0.1
0.1
0.36
0.36
±0.1
±0.5
T
A
= −40°C
to
+85°C
Guaranteed Limits
2.0
2.0
0.8
0.8
4.4
5.4
3.76
4.76
0.1
0.1
0.44
0.44
±1.0
±5.0
1.5
75
−75
40.0
µA
µA
mA
mA
mA
µA
V
Units
V
V
V
Conditions
V
OUT
=
0.1V
or V
CC
−
0.1V
V
OUT
=
0.1V
or V
CC
−
0.1V
I
OUT
= −50 µA
V
IN
=
V
IL
or V
IH
V
I
OH
=
−24
mA
I
OH
=
−24
mA (Note 5)
I
OUT
=
50
µA
V
IN
=
V
IL
or V
IH
V
I
OL
= 24 mA
I
OL
= 24 mA (Note 5)
V
I
=
V
CC
, GND
V
I
=
V
IL
, V
IH
V
O
=
V
CC
, GND
V
I
=
V
CC
−
2.1V
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
or GND
Note 5:
All outputs loaded; thresholds on input associated with output under test.
Note 6:
Maximum test duration 2.0 ms, one output loaded at a time.
AC Electrical Characteristics for AC
V
CC
Symbol
t
PLH
t
PHL
t
PLH
t
PHL
t
PZH
t
PZL
t
PHZ
t
PLZ
Parameter
Propagation Delay
S
n
to Z or Z
Propagation Delay
S
n
to Z or Z
Propagation Delay
I
n
to Z or Z
Propagation Delay
I
n
to Z or Z
Output Enable Time
OE to Z or Z
Output Enable Time
OE to Z or Z
Output Disable Time
OE to Z or Z
Output Disable Time
OE to Z or Z
Note 7:
Voltage Range 3.3 is 3.3V
±
0.3V.
Voltage Range 5.0 is 5.0V
±
0.5V
T
A
= +25°C
C
L
=
50 pF
Min
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Typ
11.5
8.5
11.0
8.0
10.0
7.0
9.0
6.5
7.5
5.5
7.5
5.5
8.5
7.0
7.0
5.5
Max
17.5
12.5
17.5
12.5
14.0
10.0
14.0
10.0
11.0
8.0
11.0
8.0
11.5
9.5
11.0
8.0
T
A
= −40°C
to
+85°C
C
L
=
50 pF
Min
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Max
19.0
13.5
19.0
13.5
15.5
11.0
15.5
11.0
12.0
9.0
12.0
9.0
13.0
10.0
12.0
8.5
ns
ns
ns
ns
ns
ns
ns
ns
Units
(V)
(Note 7)
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
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4
74AC251 • 74ACT251
AC Electrical Characteristics for ACT
V
CC
Symbol
t
PLH
t
PHL
t
PLH
t
PHL
t
PZH
t
PZL
t
PHZ
t
PLZ
Parameter
Propagation Delay
S
n
to Z or Z
Propagation Delay
S
n
to Z or Z
Propagation Delay
I
n
to Z or Z
Propagation Delay
I
n
to Z or Z
Output Enable Time
OE to Z or Z
Output Enable Time
OE to Z or Z
Output Disable Time
OE to Z or Z
Output Disable Time
OE to Z or Z
Note 8:
Voltage Range 5.0 is 5.0V
±0.5V
T
A
= +25°C
C
L
=
50 pF
Min
2.5
2.5
2.5
2.5
1.5
1.5
2.0
1.5
Typ
7.0
7.5
5.5
6.5
5.0
4.5
6.0
4.5
Max
15.5
16.5
12.0
12.5
8.5
8.5
12.0
8.5
T
A
= −40°C
to
+85°C
C
L
=
50 pF
Min
2.0
2.5
2.0
2.5
1.5
1.5
2.0
1.5
Max
17.0
18.5
13.0
14.0
9.0
9.5
13.0
9.0
ns
ns
ns
ns
ns
ns
ns
ns
Units
(V)
(Note 8)
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
Capacitance
Symbol
C
IN
C
PD
Parameter
Input Capacitance
Power Dissipation Capacitance
Typ
4.5
70.0
Units
pF
pF
V
CC
=
OPEN
V
CC
=
5.0V
Conditions
5
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