2-Input Multiplexer. 74ACT257 Datasheet

74ACT257 Multiplexer. Datasheet pdf. Equivalent

Part 74ACT257
Description Quad 2-Input Multiplexer
Feature 74AC257 • 74ACT257 Quad 2-Input Multiplexer with 3-STATE Outputs November 1988 Revised November 199.
Manufacture Fairchild Semiconductor
Datasheet
Download 74ACT257 Datasheet



74ACT257
November 1988
Revised November 1999
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
s ICC and IOZ reduced by 50%
s Multiplexer expansion by tying outputs together
s Noninverting 3-STATE outputs
s Outputs source/sink 24 mA
s ACT257 has TTL-compatible inputs
Ordering Code:
Order Number Package Number
Package Description
74AC257SC
M16A
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150Narrow 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, 0.300Wide
74ACT257SC
M16A
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150Narrow Body
74ACT257SJ
74ACT257MTC
M16D
MTC16
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
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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, 0.300Wide
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
OE
I0aI0d
I1aI1d
ZaZd
Description
Common Data Select Input
3-STATE Output Enable Input
Data Inputs from Source 0
Data Inputs from Source 1
3-STATE Multiplexer Outputs
FACTis a trademark of Fairchild Semiconductor Corporation.
© 1999 Fairchild Semiconductor Corporation DS009949
www.fairchildsemi.com



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 I0x inputs are selected and when Select
is HIGH, the I1x 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:
Za = OE (11a S + I0a S)
Zb = OE (11b S + I0b S)
Zc = OE (11c S + I0c S)
Zd = OE (11d S + I0d 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
Output
Enable
OE
H
L
L
L
L
Select
Input
S
X
H
H
L
L
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
Data
Inputs
I0 I1
XX
XL
XH
LX
HX
Outputs
Z
Z
L
H
L
H
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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