SN74LS85

4-Bit Magnitude
Comparator
The SN74LS85 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 http://onsemi.com
monotonic code. Three Outputs are provided: “A greater than B”
(OA > B), “A less than B” (OA < B), “A equal to B” (OA = B). Three LOW
Expander Inputs, IA > B, IA < B, IA = B, allow cascading without external POWER
gates. For proper compare operation, the Expander Inputs to the least
significant position must be connected as follows: IA < B= IA > B = L, SCHOTTKY
IA = B = H. For serial (ripple) expansion, the OA > B, OA < B and OA = B
Outputs are connected respectively to the IA > B, IA < B, and IA = 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
SN74LS85 under all possible logic conditions. The upper 11 lines 16
describe the normal operation under all conditions that will occur in a
1
single device or in a series expansion scheme. The lower five lines
describe the operation under abnormal conditions on the cascading PLASTIC
N SUFFIX
inputs. These conditions occur when the parallel expansion technique
CASE 648
is used.
• Easily Expandable
• Binary or BCD Comparison
• OA > B, OA < B, and OA = B Outputs Available
16
GUARANTEED OPERATING RANGES 1

Symbol Parameter Min Typ Max Unit SOIC

D SUFFIX
VCC Supply Voltage 4.75 5.0 5.25 V
CASE 751B
TA Operating Ambient 0 25 70 °C
Temperature Range
IOH Output Current – High – 0.4 mA
IOL Output Current – Low 8.0 mA

ORDERING INFORMATION

Device Package Shipping

SN74LS85N 16 Pin DIP 2000 Units/Box

SN74LS85D 16 Pin 2500/Tape & Reel

 Semiconductor Components Industries, LLC, 1999 1 Publication Order Number:

December, 1999 – Rev. 6 SN74LS85/D
 SN74LS85

CONNECTION DIAGRAM DIP (TOP VIEW)

VCC A3 B2 A2 A1 B1 A0 B0
16 15 14 13 12 11 10 9

NOTE:
The Flatpak version has the same
pinouts (Connection Diagram) as
the Dual In-Line Package.

1 2 3 4 5 6 7 8
B3 IA<B IA=B IA>B OA>B OA=B OA<B GND

LOADING (Note a)
PIN NAMES HIGH LOW
A0 – A3, B0 – B3 Parallel Inputs 1.5 U.L. 0.75 U.L.
IA = B A = B Expander Inputs 1.5 U.L. 0.75 U.L.
IA < B, IA > B A < B, A > B, Expander Inputs 0.5 U.L. 0.25 U.L.
OA > B A Greater than B Output 10 U.L. 5 U.L.
OA < B B Greater than A Output 10 U.L. 5 U.L.
OA = B A Equal to B Output 10 U.L. 5 U.L.

NOTES:
a) 1 TTL Unit Load (U.L.) = 40 mA HIGH/1.6 mA LOW.

LOGIC SYMBOL

10 12 13 15 9 11 14 1

A0 A1 A2 A3 B0 B1 B2 B3
4 IA>B OA>B 5
2 IA<B OA<B 7
3 IA=B OA=B 6

VCC = PIN 16
GND = PIN 8

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 SN74LS85

LOGIC DIAGRAM

(15)
A3
B3
(1)

(5)
OA>B

(13)
A2
B2
(14)
(2)
A<B (3) (6)
A=B (4) OA=B
A>B

(12)
A1
B1
(11)
(7)
OA<B

(10)
A0
B0
(9)

TRUTH TABLE
CASCADING
COMPARING INPUTS OUTPUTS
INPUTS
A3,B3 A2,B2 A1,B1 A0,B0 IA>B IA<B IA=B OA>B OA<B OA=B
A3>B3 X X X X X X H L L
A3<B3 X X X X X X L H L
A3=B3 A2>B2 X X X X X H L L
A3=B3 A2<B2 X X X X X L H L
A3=B3 A2=B2 A1>B1 X X X X H L L
A3=B3 A2=B2 A1<B1 X X X X L H L
A3=B3 A2=B2 A1=B1 A0>B0 X X X H L L
A3=B3 A2=B2 A1=B1 A0<B0 X X X L H L
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 X X H L L H
H = HIGH Level
A3=B3 A2=B2 A1=B1 A0=B0 H H L L L L L = LOW Level
A3=B3 A2=B2 A1=B1 A0=B0 L L L H H L X = IMMATERIAL

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 SN74LS85

A n3
A n2
A n1

B n3
B n2
B n1
An

Bn
A0 A1 A2 A3 B0 B1 B2 B3

A0 A1 A2 A3 B0 B1 B2 B3 A0 A1 A2 A3 B0 B1 B2 B3
L IA > B OA > B IA > B OA > B A>B
L IA < B SN74LS85 OA < B IA < B SN74LS85 OA < B A<B
H IA = B OA = B IA = B OA = B A=B
L = LOW LEVEL
H = HIGH LEVEL

Figure 1. Comparing Two n-Bit Words

APPLICATIONS

Figure 2 shows a high speed method of comparing two when comparing two 24-bit words. The parallel technique
24-bit words with only two levels of device delay. With the can be expanded to any number of bits, see Table 1.
technique shown in Figure 1, six levels of device delay result
Table 1
WORD LENGTH NUMBER OF PKGS.
1 – 4 Bits 1
5 – 24 Bits 2–6 NOTE:
25 – 120 Bits 8 – 31 The SN74LS85 can be used as a 5-bit comparator only
when the outputs are used to drive the A0–A3 and B0–B3
inputs of another SN74LS85 as shown in Figure 2 in posi-
tions #1, 2, 3, and 4.

INPUTS

(LSB) (MSB)
A0 A1 A2 A3 B0 B1 B2 B3 A20 A21 A22 A23 B20 B21 B22 B23

A0 A1 A2 A3 B0 B1 B2 B3 A0 A1 A2 A3 B0 B1 B2 B3
L IA > B OA > B A19 IA > B OA > B
L IA < B #5 OA < B B19 IA < B #1 OA < B
H IA = B OA = B L IA = B OA = B NC

INPUTS

A5 A6 A7 A8 B5 B6 B7 B8 A10 A11 A12 A13 B10 B11 B12 B13 A15 A16 A17 A18 B15 B16 B17 B18

A0 A1 A2 A3 B0 B1 B2 B3 A0 A1 A2 A3 B0 B1 B2 B3 A0 A1 A2 A3 B0 B1 B2 B3
A4 IA > B OA > B A9 IA > B OA > B A14 IA > B OA > B
B4 IA < B #4 OA < B B9 IA < B #3 OA < B B14 IA < B #2 OA < B
L IA = B OA = B NC L IA = B OA = B NC L IA = B OA = B NC

A0 A1 A2 A3 B0 B1 B2 B3
IA > B OA > B
IA < B #6 OA < B OUTPUTS
IA = B OA = B

MSB = MOST SIGNIFICANT BIT

LSB = LEAST SIGNIFICANT BIT
L = LOW LEVEL
H = HIGH LEVEL
NC = NO CONNECTION

Figure 2. Comparison of Two 24-Bit Words

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 SN74LS85

DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)

Limits
Symbol Parameter Min Typ Max Unit Test Conditions
Guaranteed Input HIGH Voltage for
VIH Input HIGH Voltage 2.0 V
All Inputs
0.8 Guaranteed Input LOW Voltage for
VIL Input LOW Voltage V
All Inputs
VIK Input Clamp Diode Voltage – 0.65 – 1.5 V VCC = MIN, IIN = – 18 mA
2.7 3.5 V VCC = MIN, IOH = MAX, VIN = VIH
VOH Output HIGH Voltage
or VIL per Truth Table

0.25 0.4 V IOL = 4.0 mA VCC = VCC MIN,

VOL
O Output LOW Voltage VIN = VIL or VIH
0.35 0.5 V IOL = 8.0 mA per Truth Table

Input HIGH Current

A < B, A > B 20 µA VCC = MAX, VIN = 2.7 V
IIH Other Inputs 60
A < B, A > B 0.1
mA VCC = MAX, VIN = 7.0 V
Other Inputs 0.3

Input LOW Current

IIL A < B, A > B – 0.4 mA VCC = MAX, VIN = 0.4 V
Other Inputs – 1.2
IOS Output Short Circuit Current (Note 1) – 20 –100 mA VCC = MAX
ICC Power Supply Current 20 mA VCC = MAX
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.

AC CHARACTERISTICS (TA = 25°C, VCC = 5.0 V)

Limits
Symbol Parameter Min Typ Max Unit Test Conditions
tPLH Any A or B to A < B, A > B 24 36 ns
tPHL 20 30

tPLH Any A or B to A = B 27 45 ns
tPHL 23 45

tPLH A < B or A = B to A > B 14 22 ns VCC = 5.0 V

tPHL 11 17 CL = 15 pF
tPLH A = B to A = B 13 20 ns
tPHL 13 26

tPLH A > B or A = B to A < B 14 22 ns

tPHL 11 17

AC WAVEFORMS

1.3 V 1.3 V VIN 1.3 V 1.3 V

VIN
tPHL tPLH tPHL tPLH
VOUT
1.3 V 1.3 V VOUT 1.3 V 1.3 V

Figure 3. Figure 4.

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 SN74LS85

PACKAGE DIMENSIONS

N SUFFIX
PLASTIC PACKAGE
CASE 648–08
ISSUE R
NOTES:
–A– 1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
16 9 3. DIMENSION L TO CENTER OF LEADS WHEN
FORMED PARALLEL.
B 4. DIMENSION B DOES NOT INCLUDE MOLD FLASH.
1 8 5. ROUNDED CORNERS OPTIONAL.
INCHES MILLIMETERS
DIM MIN MAX MIN MAX
F C L A 0.740 0.770 18.80 19.55
B 0.250 0.270 6.35 6.85
S C 0.145 0.175 3.69 4.44
D 0.015 0.021 0.39 0.53
SEATING F 0.040 0.70 1.02 1.77
–T– PLANE G 0.100 BSC 2.54 BSC
H 0.050 BSC 1.27 BSC
H K M J 0.008 0.015 0.21 0.38
J K 0.110 0.130 2.80 3.30
G L 0.295 0.305 7.50 7.74
D 16 PL
M 0_ 10 _ 0_ 10 _
0.25 (0.010) M T A M S 0.020 0.040 0.51 1.01

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 SN74LS85

PACKAGE DIMENSIONS

D SUFFIX
PLASTIC SOIC PACKAGE
CASE 751B–05
ISSUE J

–A–
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
16 9 2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE
–B– MOLD PROTRUSION.
P 8 PL
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
1 8
0.25 (0.010) M B S PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 (0.005) TOTAL
IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION.
G
MILLIMETERS INCHES
DIM MIN MAX MIN MAX
F A 9.80 10.00 0.386 0.393
K R X 45 _ B 3.80 4.00 0.150 0.157
C 1.35 1.75 0.054 0.068
D 0.35 0.49 0.014 0.019
C F 0.40 1.25 0.016 0.049
–T– SEATING G 1.27 BSC 0.050 BSC
PLANE
M J J 0.19 0.25 0.008 0.009
K 0.10 0.25 0.004 0.009
D 16 PL M 0_ 7_ 0_ 7_
P 5.80 6.20 0.229 0.244
0.25 (0.010) M T B S A S R 0.25 0.50 0.010 0.019

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 SN74LS85

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