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© 2000 Fairchild Semiconductor Corporation DS006379 www.fairchildsemi.com
August 1986
Revised March 2000
DM74LS85 4-Bit Magnitude Comparator
DM74LS85
4-Bit Magnitude Comparator
General Description
These 4-bit magnitude comparators perform comparison of
straight binary or BCD cod es. Three fully-decoded decisions about two, 4-bit words (A, B) are made and are externally available at three outputs. These devices are fully
expandable to any nu mber of bits without ex ternal gates.
Words of greater length may be compa red by connecting
comparators in cascade. The A > B, A < B, a nd A = B outputs of a stage handlin g l e ss-sig nifi ca nt b its a re connected
to the corresponding inputs of the next stage handling
more-significant bits. The stage handling the leastsignificant bits must ha ve a high-level voltage applied to
the A = B input. The cascading path is implem ented with
only a two-gate-level delay to reduce overall compar ison
times for long words.
Features
■ Typical power dissipation 52 mW
■ Typical delay (4-bit words) 24 ns
Ordering Code:
Devices also availab le in Tape and Reel. Specify by appending th e s uffix let t er “X” to the ordering code.
Connection Diagram
Order Number Package Number Package Description
DM74LS85M M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
DM74LS85N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
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DM74LS85
Function Table
H = HIGH Level, L = LOW Level, X = Don’t Care
Logic Diagram
Comparing Cascading Outputs
Inputs Inputs
A3, B3 A2, B2 A1, B1 A0, B0 A > BA < BA = BA > BA < BA = B
A3 > B3X X X XXXHLL
A3 < B3X X X XXXLHL
A3 = B3 A2 > B2X X XXXHLL
A3 = B3 A2 < B2X X XXXLHL
A3 = B3 A2 = B2 A1 > B1X XXXHLL
A3 = B3 A2 = B2 A1 < B1X XXXLHL
A3 = B3 A2 = B2 A1 = B1 A0 > B0XXXHLL
A3 = B3 A2 = B2 A1 = B1 A0 < B0XXXLHL
A3 = B3 A2 = B2 A1 = B1 A0 = B0 H L L H L L
A3 = B3 A2 = B2 A1 = B1 A0 = B0 L H L L H L
A3 = B3 A2 = B2 A1 = B1 A0 = B0 L L H L L H
A3 = B3 A2 = B2 A1 = B1 A0 = B0 X X H L L H
A3 = B3 A2 = B2 A1 = B1 A0 = B0HHLLLL
A3 = B3 A2 = B2 A1 = B1 A0 = B0LLLHHL
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DM74LS85
Absolute Maximum Ratings(Note 1)
Note 1: The “Absolute Maximum Ratings ” are those val ues beyond w hich
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 “Recommend ed O peratin g Cond itions” t able w ill defin e the condition s
for actual device operation.
Recommended Operating Conditions
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Note 2: All typicals are at VCC = 5V, TA = 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.
Supply Voltage 7V
Input Voltage 7V
Operating Free Air Temperature Range 0°C to +70°C
Storage Temperature Range −65°C to +150°C
Symbol Parameter Min Nom Max Units
V
CC
Supply Voltage 4.75 5 5 .25 V
V
IH
HIGH Level Input Voltage 2 V
V
IL
LOW Level Input Voltage 0.8 V
I
OH
HIGH Level Output Current −0.4 mA
I
OL
LOW Level Output Current 8 mA
T
A
Free Air Operating Temperature 0 70 °C
Symbol Parameter Conditions Min
Typ
Max Units
(Note 2)
V
I
Input Clamp Voltage VCC = Min, II = −18 mA −1.5 V
V
OH
HIGH Level VCC = Min, IOH = Max
2.7 3.4 V
Output Voltage VIL = Max, VIH = Min
V
OL
LOW Level VCC = Min, IOL = Max
0.35 0.5
Output Voltage VIL = Max, VIH = Min V
IOL = 4 mA, VCC = Min 0.25 0.4
I
I
Input Current @ Max VCC = Max A < B 0.1
Input Voltage VI = 7V A > B 0.1 mA
Others 0.3
I
IH
HIGH Level VCC = Max A < B20
Input Current VI = 2.7V A > B20µA
Others 60
I
IL
LOW Level VCC = Max A < B −0.4
Input Current VI = 0.4V A > B −0.4 mA
Others −1.2
I
OS
Short Circuit Output Current VCC = Max (Note 3) −20 −100 mA
I
CC
Supply Current VCC = Max (Note 4) 10 20 mA
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DM74LS85
Switching Characteristics
at VCC = 5V and TA = 25°C
From To Number of
RL = 2 kΩ
Symbol Parameter Input Output Gate Levels CL = 15 pF CL = 50 pF Units
Min Max Min Max
t
PLH
Propagation Delay Time Any A or B A < B,
33642
LOW-to-HIGH Level Output Data Input A > Bns
A = B 4 40 40
t
PHL
Propagation Delay Time Any A or B A < B,
33040
HIGH-to-LOW Level Output Data Input A > Bns
A = B 4 30 40
t
PLH
Propagation Delay Time
A < B or A = BA > B 1 22 26 ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
A < B or A = BA > B 1 17 26 ns
HIGH-to-LOW Level Output
t
PLH
Propagation Delay Time
A = B A = B 2 20 25 ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
A = BA = B 2 17 26 ns
HIGH-to-LOW Level Output
t
PLH
Propagation Delay Time
A > B or A = BA < B 1 22 26 ns
LOW-to-HIGH Level Output
t
PHL
Propagation Delay Time
A > B or A = BA < B 1 17 26 ns
HIGH-to-LOW Level Output
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DM74LS85
Physical Dimensions inches (millimeters) unless otherwise noted
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
Package Number M16A
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DM74LS85 4-Bit Magnitude Comparator
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Package Number N16E
Fairchild does not assume any responsibility for use of any circuitry described, no circuit pate nt licenses are implied and
Fairchild reserves the right at any time without notice to change said circuitry and specifications.
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FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or syste ms
which, (a) are intended for surgical implant into the
body, or (b) support or sustain life, and (c) whose failure
to perform when properly used in accordance with
instructions for use provided in the labeling, can be reasonably expected to result in a significant inju ry to the
user.
2. A critical component i n any compon ent of a lif e support
device or system whose failu re to perform can be reasonably expected to ca use the fa i lure of the life su pp ort
device or system, or to affect its safety or effectiveness.
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