MM54HCT251 MM74HCT251 8-Channel TRI-STATE Multiplexer
November 1995
MM54HCT251 MM74HCT251
8-Channel TRI-STATE Multiplexer
General Description
This 8-channel digital multiplexer with TRI-STATE outputs
utilizes advanced silicon-gate CMOS technology Along with
the high noise immunity and low power consumption of
standard CMOS integrated circuits it possesses the ability
to drive 10 LS-TTL loads The large output drive capability
and TRI-STATE feature make this part ideally suited for in-
terfacing with bus lines in a bus oriented system
This multiplexer features both true (Y) and complement (W)
outputs as well as a STROBE input The STROBE must be
at a low logic level to enable this device When the STROBE
input is high both outputs are in the high impedance state
When enabled address information on the data select in-
puts determines which data input is routed to the Y and W
outputs
MM54HCT MM74HCT devices are intended to interface be-
tween TTL and NMOS components and standard CMOS
devices These parts are also plug-in replacements for LS-
TTL devices and can be used to reduce power consumption
in existing designs
Features
Y
Y
Y
Y
Y
Typical propagation delay 20 ns
Low quiescent current 40
mA
maximum (74HCT Series)
Low input current 1
mA
maximum
Fanout of 10 LS-TTL loads
TTL input compatible
Connection and Logic Diagrams
Dual-in-Line Package
Truth Table
Inputs
Select
C
X
L
L
L
L
H
H
H
H
B
X
L
L
H
H
L
L
H
H
A
X
L
H
L
H
L
H
L
H
Strobe
S
H
L
L
L
L
L
L
L
L
Outputs
Y
Z
D0
D1
D2
D3
D4
D5
D6
D7
W
Z
D0
D1
D2
D3
D4
D5
D6
D7
TL F 9401 鈥?1
Top View
Order Number MM54HCT251 or MM74HCT251
H
e
high logic level L
e
logic level
X
e
irrelevant Z
e
high impedance (off)
D0 D1
D7
e
the level of the respective D input
TL F 9401 鈥?2
TRI-STATE is a registered trademark of National Semiconductor Corporation
C
1995 National Semiconductor Corporation
TL F 9401
RRD-B30M115 Printed in U S A
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