SN54LS490, SN74LS490

DUAL 4-BIT DECADE COUNTERS

SDLS125A – OCTOBER 1976 – REVISED JULY 1998

1

POST OFFICE BOX 655303

SN74LS90 Counters

Inputs for Each Decade Counter

System Densities as Package Count Can

Be Reduced by 50%

25 MHz . . . 35 MHz Typical

Collector Commutation

Small-Outline (D) Packages, Ceramic Flat

(W) Packages, Ceramic Chip Carriers (FK),

and Standard Plastic (N) and Ceramic (J)

DIPs

description

Each of these monolithic circuits contains eight

master-slave flip-flops and additional gating to

implement two individual 4-bit decade counters in

a single package. Each decade counter has

individual clock (1CLK, 2CLK), clear (1CLR,

2CLR), and set-to-9 (1SET9, 2SET9) inputs. BCD

count

sequences

of

any

length

up

to

divide-by-100 can be implemented with a single

’LS490 device. Buffering on each output is

provided to significantly reduce susceptibility to

collector commutation. All inputs are diode

clamped to reduce the effects of line ringing. The

counters have parallel outputs from each counter

stage so that submultiples of the input count

frequency are available for system timing signals.

The SN54LS490 is characterized for operation over the full military temperature range of –55

°C to 125°C.

The SN74LS490 is characterized for use in industrial systems operating from 0

°C to 70°C.

CLEAR/SET-TO-9 FUNCTION TABLE

(each counter)

INPUTS

OUTPUTS

CLR

SET9

QA

QB

QC

QD

H

L

L

L

L

L

L

HH

LL

H

L

L

Count

Copyright

© 1998, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

1CLK

1CLR

1SET9

GND

2CLK

2CLR

2SET9

SN54LS490 ...J OR W PACKAGE

SN74LS490 ...D OR N PACKAGE

(TOP VIEW)

32

1 20 19

910 11 12 13

4

5

6

7

8

18

17

16

15

14

2CLR

NC

2SET9

1SET9

NC

SN54LS490 . . . FK PACKAGE

(TOP VIEW)

NC – No internal connection