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STMicroelectronics |
November 1988
Revised November 1999
74AC157 • 74ACT157
Quad 2-Input Multiplexer
General Description
The AC/ACT157 is a high-speed quad 2-input multiplexer.
Four bits of data from two sources can be selected using
the common Select and Enable inputs. The four outputs
present the selected data in the true (noninverted) form.
The AC/ACT157 can also be used as a function generator.
Features
s ICC and IOZ reduced by 50%
s Outputs source/sink 24 mA
s ACT157 has TTL-compatible inputs
Ordering Code:
Order Number Package Number
Package Description
74AC157SC
M16A
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150” Narrow Body
74AC157SJ
M16D
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74AC157MTC
MTC16
16 -Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
74AC157PC
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
74ACT157SC
M16A
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150” Narrow Body
74ACT157SJ
M16D
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74ACT157MTC
MTC16
16 -Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
74ACT157PC
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
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
I0a–I0d
I1a–I1d
E
S
Za–Zd
Description
Source 0 Data Inputs
Source 1 Data Inputs
Enable Input
Select Input
Outputs
FACT is a trademark of Fairchild Semiconductor Corporation.
© 1999 Fairchild Semiconductor Corporation DS009929
www.fairchildsemi.com
Functional Description
The AC/ACT157 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 AC/ACT157 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 AC/ACT157 is the moving of data
from two groups of registers to four common output bus-
ses. 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 AC/ACT157 can gener-
ate any four of the sixteen different functions of two vari-
ables with one variable common. This is useful for
implementing gating functions.
Truth Table
Inputs
ES
HX
LH
LH
LL
LL
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
I0
X
X
X
L
H
Logic Diagram
Outputs
I1 Z
XL
LL
HH
XL
XH
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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