54LS85 Datasheet, PDF (1/8 Pages) National Semiconductor (TI) – 4-Bit Magnitude Comparators

June 1989
54LS85 DM54LS85 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 compara-
tors in cascade The A ^l B A ^k B and A e B outputs of a
stage handling less-significant bits are connected to the cor-
responding inputs of the next stage handling more-signifi-
cant bits The stage handling the least-significant bits must
have a high-level voltage applied to the A e B input The
cascading path is implemented with only a two-gate-level
delay to reduce overall comparison times for long words
Features
Y _{Typical power dissipation 52 mW}
Y _{Typical delay (4-bit words) 24 ns}
Y _{Alternate Military Aerospace device (54LS85) is avail-}
able Contact a National Semiconductor Sales Office
Distributor for specifications
Connection Diagram
Dual-In-Line Package
Order Number 54LS85DMQB
54LS85FMQB 54LS85LMQB
DM54LS85J DM54LS85W
DM74LS85M or DM74LS85N
See NS Package Number E20A
J16A M16A N16E or W16A
Function Table
Comparing
Inputs
A3 B3
A2 B2
A1 B1
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
A3 e B3
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
A2 e B2
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
A1 e B1
H e High Level L e Low Level X e Don’t Care
C1995 National Semiconductor Corporation TL F 6379
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
A0 e B0
TL F 6379 – 1
Cascading
Inputs
A^lB A^kB AeB
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
H
L
L
L
H
L
L
L
H
X
X
H
H
H
L
L
L
L
Outputs
A^lB
H
L
H
L
H
L
H
L
H
L
L
L
L
H
A^kB
L
H
L
H
L
H
L
H
L
H
L
L
L
H
AeB
L
L
L
L
L
L
L
L
L
L
H
H
L
L
RRD-B30M105 Printed in U S A