74LS90

Decade and Binary Counters

General Description

Each of these monolithic counters contains four master-

slave flip-flops and additional gating to provide a divide-by-

two counter and a three-stage binary counter for which the

count cycle length is divide-by-five for the DM74LS90.

All of these counters have a gated zero reset and the

DM74LS90 also has gated set-to-nine inputs for use in

BCD nine’s complement applications.

To use their maximum count length (decade or four bit

binary), the B input is connected to the QA output. The

input count pulses are applied to input A and the outputs

are as described in the appropriate truth table. A symmetri-

cal

divide-by-ten

count

can

be

obtained

from

the

DM74LS90 counters by connecting the QD output to the A

input and applying the input count to the B input which

gives a divide-by-ten square wave at output QA.

Features

s Typical power dissipation 45 mW

s Count frequency 42 MHz

Ordering Code:

Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.

Connection Diagram

Reset/Count Truth Table

Order Number

Package Number

Package Description

DM74LS90M

M14A

14-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-120, 0.150 Narrow

DM74LS90N

N14A

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

Reset Inputs

Output

R0(1)

R0(2)

R9(1)

R9(2)

QD

QC

QB

QA

H

H

L

X

LLLL

H

H

X

L

LLLL

XX

H

H

H

L

L

H

X

L

X

L

COUNT

L

X

L

X

COUNT

L

X

X

L

COUNT

X

L

L

X

COUNT

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