74F258A View Datasheet(PDF) - Fairchild Semiconductor
Part Name
Description
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74F258A Datasheet PDF : 6 Pages
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Unit Loading/Fan Out
Pin Names
S
OE
I0a–I0d
I1a–I1d
Za–Zd
Description
Common Data Select Input
3-STATE Output Enable Input (Active LOW)
Data Inputs from Source 0
Data Inputs from Source 1
3-STATE Inverting Data Outputs
U.L.
HIGH/LOW
1.0/1.0
1.0/1.0
1.0/1.0
1.0/1.0
150/40 (33.3)
Input IIH/IIL
Output IOH/IOL
20 µA/−0.6 mA
20 µA/−0.6 mA
20 µA/−0.6 mA
20 µA/−0.6 mA
−3 mA/24 mA (20 mA)
Truth Table
Output Select
Enable Input
OE
S
H
X
L
H
L
H
L
L
L
L
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
Data
Inputs
I0
I1
X
X
X
L
X
H
L
X
H
X
Output
Z
Z
H
L
H
L
Functional Description
The 74F258A is a quad 2-input multiplexer with 3-STATE
outputs. It selects four bits of data from two sources under
control of a common Select input (S). 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 inverted form.
The 74F258A 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 equation for the outputs is shown below:
Z n = OE • (I1n • S + I0n • S)
When the Output Enable input (OE) is HIGH, the outputs
are forced to a high impedance OFF state. If the outputs of
the 3-STATE devices are tied together, all but one device
must be in the high impedance state to avoid high currents
that would exceed the maximum ratings. Designers should
ensure that Output Enable signals to 3-STATE devices
whose outputs are tied together are designed so there is
no overlap.
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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