MM54HC85 MM74HC85 4-Bit Magnitude Comparator
November 1995
MM54HC85 MM74HC85
4-Bit Magnitude Comparator
General Description
The MM54HC85 MM74HC85 is a 4-bit magnitude compara-
tor that utilizes advanced silicon-gate CMOS technology It
is designed for high speed comparison of two four bit words
This circuit has eight comparison inputs 4 for each word
three cascade inputs (A
k
B A
l
B A
e
B) and three deci-
sion outputs (A
k
B A
l
B A
e
B) The result of a comparison
is indicated by a high level on one of the decision outputs
Thus it may be determined whether one word is 鈥樷€榞reater
than 鈥欌€?鈥樷€榣ess than 鈥欌€?or 鈥樷€榚qual to鈥欌€?the other word By con-
necting the outputs of the least significant stage to the cas-
cade inputs of the next stage words of greater than four bits
can be compared In addition the least significant stage
must have a high level applied to the A
e
B input and a low
level to the A
k
B and A
l
B inputs
The comparator鈥檚 outputs can drive 10 low power Schottky
TTL (LS-TTL) equivalent loads and is functionally and pin
equivalent to the 54LS85 74LS85 All inputs are protected
from damage due to static discharge by diodes to V
CC
and
ground
Features
Y
Y
Y
Y
Y
Typical propagation delay 27 ns
Wide operating voltage range 2 鈥?6V
Low input current 1
mA
maximum
Low quiescent current 80
mA
maximum (74HC Series)
Output drive capability 10 LS-TTL loads
Connection Diagram
Dual-In-Line Package
TL F 5205 鈥?1
Order Number MM54HC85 or MM74HC85
Truth Table
Comparing
Inputs
A3 B3
A3
l
B3
A3
k
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A3
e
B3
A2 B2
X
X
A2
l
B2
A2
k
B2
A2
e
B2
A2
e
B2
A2
e
B2
A2
e
B2
A2
e
B2
A2
e
B2
A2
e
B2
A2
e
B2
A2
e
B2
A1 B1
X
X
X
X
A1
l
B1
A1
k
B1
A1
e
B1
A1
e
B1
A1
e
B1
A1
e
B1
A1
e
B1
A1
e
B1
A1
e
B1
A0 B0
X
X
X
X
X
X
A0
l
B0
A0
k
B0
A0
e
B0
A0
e
B0
A0
e
B0
A0
e
B0
A0
e
B0
A
l
B
X
X
X
X
X
X
X
X
H
L
X
H
L
Cascading
Inputs
A
k
B
X
X
X
X
X
X
X
X
L
H
X
H
L
A
e
B
X
X
X
X
X
X
X
X
L
L
H
L
L
A
l
B
H
L
H
L
H
L
H
L
H
L
L
L
H
Outputs
A
k
B
L
H
L
H
L
H
L
H
L
H
L
L
H
A
e
B
L
L
L
L
L
L
L
L
L
L
H
L
L
C
1995 National Semiconductor Corporation
TL F 5205
RRD-B30M115 Printed in U S A
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