MC3456
APPLICATIONS INFORMATION
Tone Burst Generator
Dual Astable Multivibrator
For a tone burst generator, the first timer is used as a
monostable and determines the tone duration when
triggered by a positive pulse at Pin 6. The second timer is
enabled by the high output of the monostable. It is connected
as an astable and determines the frequency of the tone.
This dual astable multivibrator provides versatility not
available with single timer circuits. The duty cycle can be
adjusted from 5% to 95%. The two outputs provide two
phase clock signals often required in digital systems. It can
also be inhibited by use of either reset terminal.
+ 15 V
Reset
4
14
V
CC
14
V
R
A
R
CC
T
13 Discharge
12 Threshold
10
6
5
Trigger
Trigger
1
R
B
Output
Reset
1/2
1/2
MC3456
MC3456
Discharge
2
8
Trigger
Control
3
9
11
Control
Output
Threshold
0.01 μF
0.01 mF
7
Gnd
C2
7
Gnd
f =
C1−
Gnd
1.44
t = 1.1 R C1
T
(R + 2R ) C
A B
Figure 20. Tone Burst Generator
+15 V
10 k
Reset
4
10 k
1N914
1N914
14
10
Reset
R2
R1
2
5
9
12
Output
Threshold
Output
Threshold
1/2
1/2
MC3456
MC3456
0.001
0.001
13
1
6
8
Discharge
Trigger
Discharge
Trigger
Control
Voltage
Control
Voltage
11
3
7
Gnd
C1
Output
C2
Gnd
0.91
(R1 + R2) C
R2
f =
for C1 = C2
Duty Cycle
R1 + R2
Figure 21. Dual Astable Multivibrator
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