DM74LS85 4-Bit Magnitude Comparator
August 1986
Revised March 2000
DM74LS85
4-Bit Magnitude Comparator
General Description
These 4-bit magnitude comparators perform comparison of
straight binary or BCD codes. Three fully-decoded deci-
sions about two, 4-bit words (A, B) are made and are exter-
nally available at three outputs. These devices are fully
expandable to any number of bits without external gates.
Words of greater length may be compared by connecting
comparators in cascade. The A
>
B, A
<
B, and A
=
B out-
puts of a stage handling less-significant bits are connected
to the corresponding inputs of the next stage handling
more-significant bits. The stage handling the least-
significant bits must have a high-level voltage applied to
the A
=
B input. The cascading path is implemented with
only a two-gate-level delay to reduce overall comparison
times for long words.
Features
s
Typical power dissipation 52 mW
s
Typical delay (4-bit words) 24 ns
Ordering Code:
Order Number
DM74LS85M
DM74LS85N
Package Number
M16A
N16E
Package Description
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Connection Diagram
© 2000 Fairchild Semiconductor Corporation
DS006379
www.fairchildsemi.com
DM74LS85
Absolute Maximum Ratings
(Note 1)
Supply Voltage
Input Voltage
Operating Free Air Temperature Range
Storage Temperature Range
7V
7V
0°C to
+70°C
−65°C
to
+150°C
Note 1:
The “Absolute Maximum Ratings” are those values beyond which
the safety of the device cannot be guaranteed. The device should not be
operated at these limits. The parametric values defined in the Electrical
Characteristics tables are not guaranteed at the absolute maximum ratings.
The “Recommended Operating Conditions” table will define the conditions
for actual device operation.
Recommended Operating Conditions
Symbol
V
CC
V
IH
V
IL
I
OH
I
OL
T
A
Supply Voltage
HIGH Level Input Voltage
LOW Level Input Voltage
HIGH Level Output Current
LOW Level Output Current
Free Air Operating Temperature
0
Parameter
Min
4.75
2
0.8
−0.4
8
70
Nom
5
Max
5.25
Units
V
V
V
mA
mA
°C
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Symbol
V
I
V
OH
V
OL
Parameter
Input Clamp Voltage
HIGH Level
Output Voltage
LOW Level
Output Voltage
I
I
Input Current @ Max
Input Voltage
I
IH
HIGH Level
Input Current
I
IL
LOW Level
Input Current
I
OS
I
CC
Short Circuit Output Current
Supply Current
Conditions
V
CC
=
Min, I
I
= −18
mA
V
CC
=
Min, I
OH
=
Max
V
IL
=
Max, V
IH
=
Min
V
CC
=
Min, I
OL
=
Max
V
IL
=
Max, V
IH
=
Min
I
OL
=
4 mA, V
CC
=
Min
V
CC
=
Max
V
I
=
7V
V
CC
=
Max
V
I
=
2.7V
V
CC
=
Max
V
I
=
0.4V
V
CC
=
Max (Note 3)
V
CC
=
Max (Note 4)
A
<
B
A
>
B
Others
A
<
B
A
>
B
Others
A
<
B
A
>
B
Others
−20
10
2.7
3.4
0.35
0.25
0.5
0.4
0.1
0.1
0.3
20
20
60
−0.4
−0.4
−1.2
−100
20
mA
mA
mA
µA
mA
Min
Typ
(Note 2)
Max
−1.5
Units
V
V
V
Note 2:
All typicals are at V
CC
=
5V, T
A
=
25°C.
Note 3:
Not more than one output should be shorted at a time, and the duration should not exceed one second.
Note 4:
I
CC
is measured with all outputs OPEN, A
=
B grounded and all other inputs at 4.5V.
3
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