© 1999 Fairchild Semiconductor Corporation DS009949 www.fairchildsemi.com
November 1988
Revised November 1999
74AC257 • 74ACT257 Quad 2-Input Multiplexer with 3-STATE Outputs
74AC257 • 74ACT257
Quad 2-Input Multiplexer with 3-STATE Outputs
General Description
The AC/ACT257 is a quad 2-input multiplexer with 3-
STATE outputs. Four bits of data from two sources can be
selected using a Common Data Select input. The four out-
puts present the selected data in true (noninverted) form.
The outputs may be switched to a high impedance state by
placing a logic HIGH on the common Output Enable (OE
)
input, allowing the outputs to interface directly with bus-ori-
ented systems.
Features
■ I
CC
and I
OZ
reduced by 50%
■ Multiplexer expansion by tying outputs together
■ Noninverting 3-STATE outputs
■ Outputs source/sink 24 mA
■ ACT257 has TTL-compatible inputs
Ordering Code:
Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering code.
Logic Symbols
IEEE/IEC
Connection Diagram
Pin Descriptions
FACT is a trademark of Fairchild Semiconductor Corporation.
Order Number Package Number Package Description
74AC257SC M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150” Narrow Body
74AC257SJ M16D 16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74AC257MTC MTC16 16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
74AC257PC N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
74ACT257SC M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150” Narrow Body
74ACT257SJ M16D 16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74ACT257MTC MTC16 16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
74ACT257PC N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
Pin Names Description
S Common Data Select Input
OE
3-STATE Output Enable Input
I
0a
–I
0d
Data Inputs from Source 0
I
1a
–I
1d
Data Inputs from Source 1
Z
a
–Z
d
3-STATE Multiplexer Outputs
www.fairchildsemi.com 2
74AC257 • 74ACT257
Functional Description
The AC/ACT257 is quad 2-input multiplexer with 3-STATE
outputs. It selects four bits of data from two sources under
control of a Common Data Select input. When the Select
input is LOW, the I
0x
inputs are selected and when Select
is HIGH, the I
1x
inputs are selected. The data on the
selected inputs appears at the outputs in true (noninverted)
form. The device is the logic implementation of a 4-pole, 2-
position switch where the position of the switch is deter-
mined by the logic levels supplied to the Select input. The
logic equations for the outputs are as follows:
Z
a
= OE • (1
1a
• S + I
0a
• S)
Z
b
= OE • (1
1b
• S + I
0b
• S)
Z
c
= OE • (1
1c
• S + I
0c
• S)
Z
d
= OE • (1
1d
• S + I
0d
• S)
When the Output Enable (OE
) is HIGH, the outputs are
forced to a high impedance state. If the outputs are tied
together, all but one device must be in the high impedance
state to avoid high currents that would exceed the maxi-
mum ratings. Designers should ensure the Output Enable
signals to 3-STATE devices whose outputs are tied
together are designed so there is no overlap.
Truth Table
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.
Output Select Data Outputs
Enable Input Inputs
OE
SI
0
I
1
Z
HXXXZ
LHXLL
LHXHH
LLLXL
LLHXH
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74AC257 • 74ACT257
Absolute Maximum Ratings(Note 1) Recommended Operating
Conditions
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.
DC Electrical Characteristics for AC
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
.
Supply Voltage (V
CC
) −0.5V to +7.0V
DC Input Diode Current (I
IK
)
V
I
= −0.5V −20 mA
V
I
= V
CC
+0.5V +20 mA
DC Input Voltage (V
I
) −0.5V to V
CC
+ 0.5V
DC Output Diode Current (I
OK
)
V
O
= −0.5V −20 mA
V
O
= V
CC
+0.5V +20 mA
DC Output Voltage (V
O
) −0.5V to V
CC
+ 0.5V
DC Output Source ort
Sink Curren (I
O
) ±50 mA
DC V
CC
or Ground Current
Per Output Pin (I
CC
or I
GND
) ±50 mA
Storage Temperature (T
STG
) −65°C to +150°C
Junction Temperature (T
J
)
PDIP 140°C
Supply Voltage (V
CC
)
AC 2.0V to 6.0V
ACT 4.5V to 5.5V
Input Voltage (V
I
)0V to V
CC
Output Voltage (V
O
)0V to V
CC
Operating Temperature (T
A
) −40°C to +85°C
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 125 mV/ns
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
Symbol Parameter
V
CC
T
A
= +25°CT
A
= −40°C to +85°C
Units Conditions
(V) Typ Guaranteed Limits
V
IH
Minimum HIGH Level 3.0 1.5 2.1 2.1 V
OUT
= 0.1V
Voltage Input 4.5 2.25 3.15 3.15 V or V
CC
− 0.1V
5.5 2.75 3.85 3.85
V
IL
Maximum LOW Level 3.0 1.5 0.9 0.9 V
OUT
= 0.1V
Voltage Input 4.5 2.25 1.35 1.35 V or V
CC
− 0.1V
5.5 2.75 1.65 1.65
V
OH
Minimum HIGH Level 3.0 2.99 2.9 2.9
Voltage Output 4.5 4.49 4.4 4.4 V I
OUT
= −50 µA
5.5 5.49 5.4 5.4
V
IN
= V
IL
or V
IH
3.0 2.56 2.46 I
OH
= −12 mA
4.5 3.86 3.76 V I
OH
= −24 mA
5.5 4.86 4.76 I
OH
= −24 mA (Note 2)
V
OL
Maximum LOW Level 3.0 0.002 0.1 0.1
Voltage Output 4.5 0.001 0.1 0.1 V I
OUT
= 50 µA
5.5 0.001 0.1 0.1
V
IN
= V
IL
or V
IH
3.0 0.36 0.44 I
OL
= 12 mA
4.5 0.36 0.44 V I
OL
= 24 mA
5.5 0.36 0.44 I
OL
= 24 mA (Note 2)
I
IN
(Note 4) Maximum Input Leakage Current 5.5 ± 0.1 ± 1.0 µAV
I
= V
CC
, GND
I
OZ
Maximum 3-STATE V
I
(OE) = V
IL
, V
IH
Leakage Current 5.5 ±0.25 ±2.5 µAV
I
= V
CC
, GND
V
O
= V
CC
, GND
I
OLD
Minimum Dynamic (Note 3) 5.5 75 mA V
OLD
= 1.65V Max
I
OHD
Output Current 5.5 −75 mA V
OHD
= 3.85V Min
I
CC
(Note 4) Maximum Quiescent Supply Current 5.5 4.0 40.0 µAV
IN
= V
CC
or GND
