MC74HC390A Datasheet, PDF (6/8 Pages) ON Semiconductor – Dual 4-Stage Binary Ripple Counter with ÷2 and ÷5 Sections

MC74HC390A
APPLICATIONS INFORMATION
Each half of the MC54/74HC390A has independent ÷ 2
and ÷ 5 sections (except for the Reset function). The ÷ 2 and
÷ 5 counters can be connected to give BCD or bi–quinary
(2–5) count sequences. If Output QA is connected to the
Clock B input (Figure 4), a decade divider with BCD output
is obtained. The function table for the BCD count sequence
is given in Table 1.
To obtain a bi–quinary count sequence, the input signals
connected to the Clock B input, and output QD is connected
to the Clock A input (Figure 5). QA provides a 50% duty
cycle output. The bi–quinary count sequence function table
is given in Table 2.
Table 1. BCD Count Sequence*
Output
Count
QD
QC
QB
QA
0
L
L
L
L
1
L
L
L
H
2
L
L
H
L
3
L
L
H
H
4
L
H
L
L
5
L
H
L
H
6
L
H
H
L
7
L
H
H
H
8
H
L
L
L
9
H
L
L
H
*QA connected to Clock B input.
Table 2. Bi–Quinary Count Sequence**
Output
Count
QA
QD
QC
QB
0
L
L
L
L
1
L
L
L
H
2
L
L
H
L
3
L
L
H
H
4
L
H
L
L
8
H
L
L
L
9
H
L
L
H
10
H
L
H
L
11
H
L
H
H
12
H
H
L
L
** QD connected to Clock A input.
CLOCK A
1, 15
÷2
COUNTER
CONNECTION DIAGRAMS
3, 13 _QA
CLOCK A
1, 15
÷2
COUNTER
3, 13 _QA
CLOCK B
RESET
4, 12
÷5
COUNTER
2, 14
5, 11 _QB
6, 10
7, 9 ^QC
QD
Figure 4. BCD Count
CLOCK B ^{4, 12}
2, 14
RESET
÷5
COUNTER
5, 11 _QB
6, 10
QC
7, 9 _QD
Figure 5. Bi-Quinary Count
http://onsemi.com
6