Motorola SN74LS85D, SN74LS85N Datasheet
5-84
FAST AND LS TTL DATA
4-BIT MAGNITUDE
COMPARATOR
The SN54/74LS85 is a 4-Bit Magnitude Camparator which compares two
4-bit words (A, B), each word having four Parallel Inputs (A0–A3, B0–B3); A3,
B3 being the most significant inputs. Operation is not restricted to binary
codes, the device will work with any monotonic code. Three Outputs are
provided: “A greater than B” (O
A>B
), “A less than B” (O
A<B
), “A equal to B”
(O
A=B
). Three Expander Inputs, I
A>B
, I
A<B
, I
A=B
, allow cascading without
external gates. For proper compare operation, the Expander Inputs to the
least significant position must be connected as follows: I
A<B
= I
A>B
= L, I
A=B
= H. For serial (ripple) expansion, the O
A>B
, O
A<B
and O
A=B
Outputs are
connected respectively to the I
A>B
, I
A<B
, and I
A=B
Inputs of the next most
significant comparator, as shown in Figure 1. Refer to Applications section of
data sheet for high speed method of comparing large words.
The Truth Table on the following page describes the operation of the
SN54/74LS85 under all possible logic conditions. The upper 11 lines describe
the normal operation under all conditions that will occur in a single device or
in a series expansion scheme. The lower five lines describe the operation
under abnormal conditions on the cascading inputs. These conditions occur
when the parallel expansion technique is used.
• Easily Expandable
• Binary or BCD Comparison
• O
A>B
, O
A<B
, and O
A=B
Outputs Available
CONNECTION DIAGRAM DIP (TOP VIEW)
NOTE:
The Flatpak version has the
same pinouts (Connection
Diagram) as the Dual In-Line
Package.
14 13 12 11 10 9
1 2 3 4 5 6
7
16 15
8
V
CC
B
3
A
3
B2A2A
1
A
0
B
1
B
0
I
A<BIA=BIA>BOA>BOA=B
O
A<B
GND
PIN NAMES LOADING (Note a)
HIGH
LOW
A0–A3, B0–B
3
I
A=B
I
A<B
, I
A>B
O
A>B
O
A<B
O
A=B
Parallel Inputs
A = B Expander Inputs
A < B, A > B, Expander Inputs
A Greater Than B Output (Note b)
B Greater Than A Output (Note b)
A Equal to B Output (Note b)
1.5 U.L.
1.5 U.L.
0.5 U.L.
10 U.L.
10 U.L.
10 U.L.
0.75 U.L.
0.75 U.L.
0.25 U.L.
5 (2.5) U.L.
5 (2.5) U.L.
5 (2.5) U.L.
NOTES:
a) 1 TTL Unit Load (U.L.) = 40 µA HIGH/1.6 mA LOW.
b) The Output LOW drive factor is 2.5 U.L. for Military (54) and 5 U.L. for Commercial (74)
Temperature Ranges.
SN54/74LS85
4-BIT MAGNITUDE
COMPARATOR
LOW POWER SCHOTTKY
J SUFFIX
CERAMIC
CASE 620-09
N SUFFIX
PLASTIC
CASE 648-08
16
1
16
1
ORDERING INFORMATION
SN54LSXXJ Ceramic
SN74LSXXN Plastic
SN74LSXXD SOIC
16
1
D SUFFIX
SOIC
CASE 751B-03
LOGIC SYMBOL
VCC = PIN 16
GND = PIN 8
10 12 1315 9 11 14 1
4
2
3
5
7
6
A0A1A2A3B0B1B2B
3
I
A>B
I
A<B
I
A=B
O
A>B
O
A<B
O
A=B
H = HIGH Level
L = LOW Level
X = IMMATERIAL
5-85
FAST AND LS TTL DATA
SN54/74LS85
LOGIC DIAGRAM
O
A>B
O
A<B
O
A=B
(5)
(6)
(7)
A3
B3
A2
B2
A<B
A=B
A>B
A1
B1
A0
B0
(15)
(1)
(13)
(14)
(12)
(11)
(10)
(9)
(2)
(3)
(4)
TRUTH TABLE
COMPARING INPUTS
CASCADING
INPUTS
OUTPUTS
A3,B3A2,B2A1,B1A0,B0I
A>BIA<BIA=BOA>BOA<BOA=B
A3>B
3
X X X X X X H L L
A3<B
3
X X X X X X L H L
A3=B3A2>B
2
X X X X X H L L
A3=B3A2<B
2
X X X X X L H L
A3=B3A2=B2A1>B
1
X X X X H L L
A3=B3A2=B2A1<B
1
X X X X L H L
A3=B3A2=B2A1=B1 A0>B
0
X X X H L L
A3=B3A2=B2A1=B1A0<B
0
X X X L H L
A3=B3A2=B2A1=B1A0=B
0
H L L H L L
A3=B3A2=B2A1=B1A0=B
0
L H L L H L
A3=B3A2=B2A1=B1A0=B
0
X X H L L H
A3=B3A2=B2A1=B1A0=B
0
H H L L L L
A3=B3A2=B2A1=B1A0=B
0
L L L H H L
GUARANTEED OPERATING RANGES
Symbol Parameter Min Typ Max Unit
V
CC
Supply Voltage 54
74
4.5
4.75
5.0
5.0
5.5
5.25
V
T
A
Operating Ambient Temperature Range 54
74
–55
0
25
25
125
70
°C
I
OH
Output Current — High 54, 74 –0.4 mA
I
OL
Output Current — Low 54
74
4.0
8.0
mA
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