Philips Semiconductors
Product specification
Quad 2-input multiplexer
74HC/HCT157
Moving the data from two groups of registers to four
common output buses is a common use of the “157”. The
state of the common data select input (S) determines the
particular register from which the data comes. It can also
be used as function generator.
FEATURES
• Non-inverting data path
• Output capability: standard
• ICC category: MSI
The device is useful for implementing highly irregular logic
by generating any four of the 16 different functions of two
variables with one variable common.
GENERAL DESCRIPTION
The 74HC/HCT157 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The “157” is the logic implementation of a 4-pole,
2-position switch, where the position of the switch is
determined by the logic levels applied to S.
The logic equations are:
1Y = E.(1l1.S + 1l0.S)
2Y = E.(2l1.S + 2l0.S)
3Y = E.(3l1.S + 3l0.S)
4Y = E.(4l1.S + 4l0.S)
The 74HC/HCT157 are quad 2-input multiplexers which
select 4 bits of data from two sources under the control of
a common data select input (S). The four outputs present
the selected data in the true (non-inverted) form. The
enable input (E) is active LOW. When E is HIGH, all of the
outputs (1Y to 4Y) are forced LOW regardless of all other
input conditions.
The “157” is identical to the “158” but has non-inverting
(true) outputs.
QUICK REFERENCE DATA
GND = 0 V; Tamb = 25 °C; tr = tf = 6 ns
TYPICAL
SYMBOL
PARAMETER
propagation delay
CONDITIONS
UNIT
HC
HCT
tPHL/ tPLH
CL = 15 pF; VCC = 5 V
nI0, nI1 to nY
E to nY
11
13
ns
ns
ns
pF
pF
11
12
19
3.5
70
S to nY
12
3.5
70
CI
input capacitance
CPD
power dissipation capacitance per multiplexer notes 1 and 2
Notes
1. CPD is used to determine the dynamic power dissipation (PD in µW):
PD = CPD × VCC2 × fi + ∑ (CL × VCC2 × fo) where:
fi = input frequency in MHz
fo = output frequency in MHz
∑ (CL × VCC2 × fo) = sum of outputs
CL = output load capacitance in pF
VCC = supply voltage in V
2. For HC the condition is VI = GND to VCC
For HCT the condition is VI = GND to VCC − 1.5 V
ORDERING INFORMATION
See “74HC/HCT/HCU/HCMOS Logic Package Information”.
December 1990
2
NXP [ NXP ]
