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” (OA> B), “A less than B” (OA< B), “A equal to B”

(OA= B). Three Expander Inputs, IA> B, IA< B, IA= B, allow cascading without

external gates. For proper compare operation, the Expander Inputs to the

least significant position must be connected as follows: IA< B= IA> B = L, 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

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.

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

VCC

B3

A3

B2

A2

A1

A0

B1

B0

IA<B IA=B IA>B OA>B OA=B OA<B GND

PIN NAMES

LOADING (Note a)

HIGH

LOW

A0 – A3, B0 – B3

IA = B

IA < B, IA > B

OA > B

OA < B

OA = 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 13 15 9 11 14 1

4

2

3

5

7

6

A0 A1 A2 A3 B0 B1 B2 B3

IA>B

IA<B

IA=B

OA>B

OA<B

OA=B