MOTOROLA SN74LS85D, SN74LS85DR2, SN74LS85M, SN74LS85MEL, SN74LS85ML1 Datasheet

 Semiconductor Components Industries, LLC, 1999

December, 1999 – Rev. 6

1 Publication Order Number:

SN74LS85/D

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
(A

0–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 T able on the following page describes the operation of the
SN74LS85 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 A vailable

GUARANTEED OPERATING RANGES

Symbol Parameter Min Typ Max Unit

V

CC

Supply Voltage 4.75 5.0 5.25 V

T

A

Operating Ambient

T emperature Range

0 25 70 °C

I

OH

Output Current – High –0.4 mA

I

OL

Output Current – Low 8.0 mA

LOW

POWER

SCHOTTKY

Device Package Shipping

ORDERING INFORMATION

SN74LS85N 16 Pin DIP 2000 Units/Box
SN74LS85D 16 Pin

SOIC

D SUFFIX

CASE 751B

http://onsemi.com

2500/Tape & Reel

PLASTIC
N SUFFIX
CASE 648

16

1

16

1

SN74LS85

http://onsemi.com

2

LOGIC SYMBOL

CONNECTION DIAGRAM DIP (TOP VIEW)

Parallel Inputs
A = B Expander Inputs
A < B, A > B, Expander Inputs
A Greater than B Output
B Greater than A Output
A Equal to B Output

A

0

– A3, B0 – B

3

I

A = B

I

A < B

, I

A > B

O

A > B

O

A < B

OA = 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 U.L.
5 U.L.
5 U.L.

NOTES:

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

HIGH LOW

(Note a)LOADING

PIN NAMES

V

CC

= PIN 16

GND = PIN 8

10 12 13 15 9 11 14 1

4
2
3

5
7
6

A

0A1A2A3B0B1B2B3

I

A>B

I

A<B

I

A=B

O

A>B

O

A<B

O

A=B

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

14 13 12 11 10 9

123456

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

H = HIGH Level
L = LOW Level
X = IMMATERIAL

SN74LS85

http://onsemi.com

3

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=B

O

A>B

O

A<B

O

A=B

A3>B

3

X X X X X X H L L

A3<B

3

XXXXXX L HL

A3=B3A2>B

2

XXXXX H LL

A3=B3A2<B

2

XXXXX L HL

A3=B3A2=B2A1>B

1

XXXX H LL

A3=B3A2=B2A1<B

1

XXXX L HL

A3=B3A2=B2A1=B1 A0>B

0

X XX H LL

A3=B3A2=B2A1=B1A0<B

0

X XX L HL

A3=B3A2=B2A1=B1A0=B

0

H LL H LL

A3=B3A2=B2A1=B1A0=B

0

L HL L HL

A3=B3A2=B2A1=B1A0=B

0

X XH L LH

A3=B3A2=B2A1=B1A0=B

0

H HL L LL

A3=B3A2=B2A1=B1A0=B

0

L L L H H L