MC14028B
http://onsemi.com
4
Figure 1. Dynamic Signal Waveforms
Inputs B, C, and D switching
in respect to a BCD code.
Inputs A, B, and D low.
All outputs connected to respective
C
L
loads. f in respect to a system clock
20 ns 20 ns
90%
50%
10%
1/f
V
DD
V
SS
20 ns 20 ns
INPUT A
INPUT C
Q4
10%
90%
50%
V
DD
V
SS
V
OH
V
OL
t
PLH
t
PHL
t
TLH
t
THL
50%
90%
10%
LOGIC DIAGRAM
Q9
Q8
Q7
Q6
Q5
Q4
Q3
Q2
Q1
Q0
D
C
B
A
APPLICATIONS INFORMATION
Expanded decoding can be performed by using the
MC14028B and other CMOS Integrated Circuits. The
circuit in Figure 2 converts any 4−bit code to a decimal or
hexadecimal code. The accompanying table shows the input
binary combinations, the associated “output numbers” that
go “high” when selected, and the “redefined output
numbers” needed for the proper code. For example: For the
combination DCBA = 0111 the output number 7 is redefined
for the 4−bit binary, 4−bit gray, excess−3, or excess−3 gray
codes as 7, 5, 4, or 2, respectively. Figure 3 shows a 6−bit
binary 1−of−64 decoder using nine MC14028B circuits and
two MC14069UB inverters.
The MC14028B can be used in decimal digit displays,
such as, neon readouts or incandescent projection indicators
as shown in Figure 4.
Figure 2. Code Conversion Circuit and Truth Table
INPUTS
D
MC14028B
CBA
DCB A DCB A
MC14028B
Q9 Q0 Q9 Q0
15 −8 15 −0
OUTPUT NUMBERS
