MC74ACT157 查看數據表（PDF） - Motorola => Freescale
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MC74ACT157 Datasheet PDF : 6 Pages
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MC74AC157 MC74ACT157
FUNCTIONAL DESCRIPTION
The MC74AC157/74ACT157 is a quad 2-input multiplexer.
It selects four bits of data from two sources under the control
of a common Select input (S). The Enable input (E) is
active-LOW. When E is HIGH, all of the outputs (Z) are forced
LOW regardless of all other inputs. The MC74AC157/
74ACT157 is the logic implementation of a 4-pole, 2-position
switch where the position of the switch is determined by the
logic levels supplied to the Select input. The logic equations for
the outputs are shown below:
Za = E•(I1a•S+I0a•S)
Zb = E•(I1b•S+I0b•S)
Zc = E•(I1c•S+I0c•S)
Zd = E•(I1d•S+I0d•S)
A common use of the MC74AC157/74ACT157 is the
moving of data from two groups of registers to four common
output busses. The particular register from which the data
comes is determined by the state of the Select input. A less
obvious use is as a function generator. The MC74AC157/
74ACT157 can generate any four of the sixteen different
functions of two variables with one variable common. This is
useful for implementing gating functions.
LOGIC DIAGRAM
I0a
I1a
I0b
I1b
I0c
I1c
I0d
I1d
E
S
Za
Zb
Zc
Zd
Please note that this diagram is provided only for the understanding of logic
operations and should not be used to estimate propagation delays.
MAXIMUM RATINGS*
Symbol
Parameter
Value
Unit
VCC
Vin
Vout
Iin
Iout
ICC
Tstg
DC Supply Voltage (Referenced to GND)
DC Input Voltage (Referenced to GND)
DC Output Voltage (Referenced to GND)
DC Input Current, per Pin
DC Output Sink/Source Current, per Pin
DC VCC or GND Current per Output Pin
Storage Temperature
–0.5 to +7.0
V
–0.5 to VCC +0.5
V
–0.5 to VCC +0.5
V
±20
mA
±50
mA
±50
mA
–65 to +150
°C
* Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the Recommended
Operating Conditions.
FACT DATA
5-2
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