Fairchild Semiconductor DM74LS90N, DM74LS90MX, DM74LS90M, DM74LS90CW Datasheet
© 2000 Fairchild Semiconductor Corporation DS006381 www.fairchildsemi.com
August 1986
Revised March 2000
DM74LS90 Decade and Binary Counters
DM74LS90
Decade and Binary Counters
General Description
Each of these monolithic counters contains four masterslave flip-flops and additio nal ga ting to pr ovid e a di vid e-b ytwo 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 Q
A
output. The
input count pulses are applied to input A and the outputs
are as described in the appropriate truth table. A symmetrical divide-by-ten count can be obtained from the
DM74LS90 counters by conne cting the Q
D
output to the A
input and applying the input count to the B input which
gives a divide-by-ten square wave at output Q
A
.
Features
■ Typical power dissipation 45 mW
■ Count frequency 42 MHz
Ordering Code:
Devices also availab le in Tape and Reel. Specify by appending th e s uffix let t er “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) Q
DQCQBQA
H H L X LLLL
H H X L LLLL
XXHHHLLH
X L X L COUNT
L X L X COUNT
L X X L COUNT
X L L X COUNT
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DM74LS90
Function Tables
BCD Count Sequence (Note 1)
Bi-Quinary (5-2) (Note 2)
H = HIGH Level
L = LOW Level
X = Don’t Care
Note 1: Output Q
A
is connected to input B for BCD count.
Note 2: Output Q
D
is connected to input A for bi-quinary count.
Note 3: Output Q
A
is connected to input B.
Logic Diagram
The J and K inputs sho wn without connec tion are for refere nce only and
are functionally at a high level.
Count Output
Q
D
Q
C
Q
B
Q
A
0 LLLL
1LLLH
2LLHL
3LLHH
4LHLL
5LHLH
6LHHL
7 LHHH
8 HLLL
9HLLH
Count Output
Q
A
Q
D
Q
C
Q
B
0 LLLL
1LLLH
2LLHL
3LLHH
4LHLL
5 HLLL
6HLLH
7HLHL
8HLHH
9HHLL
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