DM74LS85
4-Bit Magnitude Comparators
General Description
These 4-bit magnitude comparators perform comparison of
straight binary or BCD codes. Three fully-decoded decisions
about two, 4-bit words (A, B) are made and are externally
available at three outputs. These devices are fully expand-
able 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 outputs of a stage
handling less-significant bits are connected to the corre-
sponding 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 cascad-
ing path is implemented with only a two-gate-level delay to
reduce overall comparison times for long words.
Features
nTypical power dissipation 52 mW
nTypical delay (4-bit words) 24 ns
nAlternate Military/Aerospace device (54LS85) is
available. Contact a Fairchild Semiconductor Sales
Office/Distributor for specifications.
Connection Diagram
Dual-In-Line Package
DS006379-1
Order Number 54LS85DMQB, 54LS85FMQB, 54LS85LMQB, DM54LS85J, DM54LS85W, DM74LS85M or DM74LS85N
See Package Number E20A, J16A, M16A, N16E or W16A
March 1998
DM74LS85 4-Bit Magnitude Comparators
© 1998 Fairchild Semiconductor Corporation DS006379 www.fairchildsemi.com
Function Table
Comparing Cascading Outputs
Inputs Inputs
A3, B3 A2, B2 A1, B1 A0, B0 A >BA
<
BA
=
BA
>
BA
<
BA
=
B
A3 >B3XXXXXXHLL
A3 <B3XXXXXXLHL
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
H
=
High Level, L =Low Level, X =Don’t Care
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Absolute Maximum Ratings (Note 1)
Supply Voltage 7V
Input Voltage 7V
Operating Free Air Temperature Range
DM54LS and 54LS −55˚C to +125˚C
DM74LS 0˚C to +70˚C
Storage Temperature Range −65˚C to +150˚C
Recommended Operating Conditions
Symbol Parameter DM54LS85 DM74LS85 Units
Min Nom Max Min Nom Max
V
CC
Supply Voltage 4.5 5 5.5 4.75 5 5.25 V
V
IH
High Level Input Voltage 2 2 V
V
IL
Low Level Input Voltage 0.7 0.8 V
I
OH
High Level Output Current −0.4 −0.4 mA
I
OL
Low Level Output Current 4 8 mA
T
A
Free Air Operating Temperature −55 125 0 70 ˚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” table are not guaranteed at the absolute maximum ratings. The “Recommended Operating
Conditions” table will define the conditions for actual device operation.
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Symbol Parameter Conditions Min Typ Max Units
(Note 2)
V
I
Input Clamp Voltage V
CC
=Min, I
I
=−18 mA −1.5 V
V
OH
High Level Output V
CC
=Min, I
OH
=Max DM54 2.5 3.4 V
Voltage V
IL
=Max, V
IH
=Min DM74 2.7 3.4
V
OL
Low Level Output V
CC
=Min, I
OL
=Max DM54 0.25 0.4
Voltage V
IL
=Max, V
IH
=Min DM74 0.35 0.5 V
I
OL
=4 mA, V
CC
=Min DM74 0.25 0.4
I
I
Input Current @Max V
CC
=Max A <B 0.1
Input Voltage V
I
=7V A >B 0.1 mA
Others 0.3
I
IH
High Level Input V
CC
=Max A <B20
Current V
I
=2.7V A >B20µA
Others 60
I
IL
Low Level Input V
CC
=Max A <B −0.4
Current V
I
=0.4V A >B −0.4 mA
Others −1.2
I
OS
Short Circuit V
CC
=Max DM54 −20 −100 mA
Output Current (Note 3) DM74 −20 −100
I
CC
Supply Current V
CC
=Max (Note 4) 10 20 mA
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: ICC is measured with all outputs open, A =B grounded and all other inputs at 4.5V.
3 www.fairchildsemi.com
Switching Characteristics
at V
CC
=5V and T
A
=25˚C
From To Number of R
L
=2kΩ
Symbol Parameter Input Output Gate Levels C
L
=15 pF C
L
=50 pF Units
Min Max Min Max
t
PLH
Propagation Delay Time Any A or B A <B, 3 36 42
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, 3 30 40
High-to-Low Level Output Data Input A >Bns
A
=
B 4 30 40
t
PLH
Propagation Delay Time A <BA
>
B 1 22 26 ns
Low-to-High Level Output or A =B
t
PHL
Propagation Delay Time A <BA
>
B 1 17 26 ns
High-to-Low Level Output or A =B
t
PLH
Propagation Delay Time A =BA
=
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 >BA
<
B 1 22 26 ns
Low-to-High Level Output or A =B
t
PHL
Propagation Delay Time A >BA
<
B 1 17 26 ns
High-to-Low Level Output or A =B
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Logic Diagram
DS006379-2
5 www.fairchildsemi.com
Physical Dimensions inches (millimeters) unless otherwise noted
Chip Carrier Package (E)
Order Number 54LS85LMQB
Package Number E20A
16-Lead Ceramic Dual-In-Line Package (J)
Order Number 54LS85DMQB or DM54LS85J
Package Number J16A
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16-Lead Small Outline Molded Package (M)
Order Number DM74LS85M
Package Number M16A
16-Lead Molded Dual-In-Line Package (N)
Order Number DM74LS85N
Package Number N16E
7 www.fairchildsemi.com
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DE-
VICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMI-
CONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or sys-
tems 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 injury
to the user.
2. A critical component in any component of a life support
device or system whose failure to perform can be rea-
sonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
Fairchild Semiconductor
Corporation
Americas
Customer Response Center
Tel: 1-888-522-5372
www.fairchildsemi.com
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Europe Fax: +49 (0) 1 80-530 85 86
Email: europe.support@nsc.com
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Tel: +852 2737-7200
Fax: +852 2314-0061
National Semiconductor
Japan Ltd.
Tel: 81-3-5620-6175
Fax: 81-3-5620-6179
16-Lead Ceramic Flat Package (W)
Order Number 54LS85FMQB or DM54LS85W
Package Number W16A
DM74LS85 4-Bit Magnitude Comparators
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and Fairchild reserves the right at any time without notice to change said circuitry and specifications.
