74ACT253 National Semiconductor, 74ACT253 Datasheet - Page 2

• Manufacturer Part Number: 74ACT253
• Description: Dual 4-Input Multiplexer with TRI-STATE Outputs
• Manufacturer: National Semiconductor

www.national.com
Connection Diagrams
Functional Description
The ’AC/’ACT253 contains two identical 4-input multiplexers
with TRI-STATE outputs. They select two bits from four
sources selected by common Select inputs (S
4-input multiplexers have individual Output Enable (OE
OE
impedance (High Z) state. This device is the logic implemen-
tation of a 2-pole, 4-position switch, where the position of the
switch is determined by the logic levels supplied to the two
select inputs. The logic equations for the outputs are shown:
Z
Truth Table
Address Inputs S
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
a
b
= OE
S
X
H
H
H
H
L
L
L
L
) inputs which, when HIGH, force the outputs to a high
0
Select
Inputs
a
• (I
0a
0
S
X
H
H
H
H
L
L
L
L
and S
1
• S
for DIP and Flatpak
1
1
are common to both sections.
Pin Assignment
• S
I
X
H
X
X
X
X
X
X
L
0
0
+ I
Data Inputs
1a
H
I
X
X
X
X
X
X
X
L
1
• S
1
I
X
X
X
X
X
H
X
X
• S
L
2
DS100285-3
0
+
I
H
X
X
X
X
X
X
X
L
3
0
, S
Output
Enable
OE
1
H
L
L
L
L
L
L
L
L
). The
a
,
Outputs
2
Z
Z
H
H
H
H
L
L
L
L
I
Z
I
If the outputs of TRI-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. De-
signers should ensure that Output Enable signals to
TRI-STATE devices whose outputs are tied together are de-
signed so that there is no overlap.
2a
2b
b
= OE
• S
• S
1
1
• S
• S
b
• (I
0
0
+ I
0b
+ I
3a
3b
• S
• S
• S
1
Pin Assignment
• S
1
1
• S
• S
0
for LCC
+ I
0
0
)
)
1b
• S
1
• S
DS100285-4
0
+