DM74LS85MX - Fairchild Semiconductor

August 1986

Revised March 2000

DM74LS85 4-Bit Magnitude Comparator

DM74LS85

4-Bit Magnitude Comparator

General Descript ion

These 4-bit magnitude comparators perform comparison of

straight binary or BCD codes. Three fully-decoded deci-

sions about two, 4-bit words (A, B) are made and are exter-

nally available at three outputs. These devices are fully

expandable to any number of bits without external gates.

Words of greater length may be compared by connecting

comparato rs in cascad e. The A > B, A < B, a nd A = B out-

puts of a stage ha ndl in g le ss-si g nific a nt b its a re conn ect ed

to the corresponding inputs of the next stage handling

more-significant bits. The stage handling the least-

significant bits must have a high-level voltage applied to

the A =B input. The cascading path is implemented with

only a two-gate-level delay to reduce overall comparison

times for long words.

Features

■Typical power dissipation 52 mW

■Typical delay (4-bit words) 24 ns

Ordering Code:

Devices also available in Tape and Ree l. S pecify by ap pending the suffix let t er “X” to the orderin g c ode.

Connection Diagram

Order Number Package Number Package Description

DM74LS85M M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow

DM74LS85N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

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DM74LS85

Function Table

H = HIGH Level, L = LOW Level, X = Don’t Ca re

Logic Diagram

Comparing Cascading Outputs

Inputs Inputs

A3, B3 A2, B2 A1, B1 A0, B0 A > BA < BA = BA > BA < BA = B

A3 > B3X X X XXXHLL

A3 < B3X X X XXXLHL

A3 = B3 A2 > B2X X XXXHLL

A3 = B3 A2 < B2X X XXXLHL

A3 = B3 A2 = B2 A1 > B1X XXXHLL

A3 = B3 A2 = B2 A1 < B1X XXXLHL

A3 = B3 A2 = B2 A1 = B1 A0 > B0XXXHLL

A3 = B3 A2 = B2 A1 = B1 A0 < B0XXXLHL

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 L L H L L H

A3 = B3 A2 = B2 A1 = B1 A0 = B0 X X H L L H

A3 = B3 A2 = B2 A1 = B1 A0 = B0HHLLLL

A3 = B3 A2 = B2 A1 = B1 A0 = B0LLLHHL

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DM74LS85

Absolute Maxim um Ratings(Note 1) Note 1: The “A bsolute Ma ximum Ratin gs” are those values beyon d which

the safety of the device cannot be guaranteed. The device should not be

operated at these limits. The parametric values defined in the Electrical

Characteristics tables are not guaranteed at the absolute maximum ratings.

The “Re comm ended Operat ing Co ndition s” table will de fine the cond itions

for actu al device operation.

Recommended Operating Conditions

Electri cal Characteristics

over recommended operating free air temperature range (unless otherwise noted)

Note 2: All typicals are at VCC = 5V, TA = 25°C.

Note 3: N ot m ore than one output sh ould be sh orted at a tim e, and the duration sh ould not ex c eed one sec ond.

Note 4: ICC is measured with all outputs OPEN, A = B grounded and all ot her inputs at 4. 5V.

Supply Voltage 7V

Input Voltage 7V

Operating Free Air Temperature Range 0°C to +70°C

Storage Temperature Range −65°C to +150°C

Symbol Parameter Min Nom Max Units

VCC Supply Voltage 4.75 5 5.25 V

VIH HIGH Level Input Voltage 2 V

VIL LOW Level Input Voltage 0.8 V

IOH HIGH Level Output Current −0.4 mA

IOL LOW Level Output Current 8 mA

TAFree Air Operating Temperature 0 70 °C

Symbol Parameter Conditions Min Typ Max Units

(Note 2)

VIInput Clamp Voltage VCC = Min, II = −18 mA −1.5 V

VOH HIGH Level VCC = Min, IOH = Max 2.7 3.4 V

Output Voltage VIL = Max, VIH = Min

VOL LOW Level VCC = Min, I OL = Max 0.35 0.5

Output Voltage VIL = Max, VIH = Min V

IOL = 4 mA, VCC = Min 0.25 0.4

IIInput Current @ Max VCC = Max A < B 0.1

Input V oltag e VI = 7V A > B 0.1 mA

Others 0.3

IIH HIGH Level VCC = Max A < B20

Input Current VI = 2.7V A > B20µA

Others 60

IIL LOW Level VCC = Max A < B −0.4

Input Current VI = 0.4V A > B −0.4 mA

Others −1.2

IOS Short Circuit Output Current VCC = Max (Note 3) −20 −100 mA

ICC Supply Current VCC = Max (Note 4) 10 20 mA

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DM74LS85

Switching Characteri stics

at VCC = 5V and TA = 25°C From To Num ber of RL = 2 kΩ

Symbol Parameter Input Output Gate Levels CL = 15 pF CL = 50 pF Units

Min Max Min Max

tPLH Propagation Delay Time Any A or B A < B, 33642

LOW-to-HIGH Level Output Data Input A > Bns

A = B 4 40 40

tPHL Propagation Delay Time Any A or B A < B, 33040

HIGH-to-LOW Level Output Data Input A > Bns

A = B 4 30 40

tPLH Propagation Delay Time A < B or A = BA > B 1 22 26 ns

LOW-to-HIGH Level Output

tPHL Propagation Delay Time A < B or A = BA > B 1 17 26 ns

HIGH-to-LOW Level Output

tPLH Propagation Delay Time A = B A = B 2 20 25 ns

LOW-to-HIGH Level Output

tPHL Propagation Delay Time A = BA = B 2 17 26 ns

HIGH-to-LOW Level Output

tPLH Propagation Delay Time A > B or A = BA < B 1 22 26 ns

LOW-to-HIGH Level Output

tPHL Propagation Delay Time A > B or A = BA < B 1 17 26 ns

HIGH-to-LOW Level Output

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DM74LS85

Physical Dim ensions inches (millimeters) unless otherwise noted

16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow

Package Number M16A

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DM74LS85 4-Bit Magnitude Comparator

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide

Package Number N16E

Fairchild does no t assume any responsibility for use of any c ircuitry described, no circuit pate nt licenses are implied and

Fairchild reserves the right at any time without notice to change said circuitry and specifications.

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