TS3V556

6/8

V

CC

Reset

Out

R

C

R

A

B

Control

Voltage

0.01 F

µ

TS3V556

Figure 4

Ω

Ω

µ

t = 0.5 ms / div

OUTPUT VOLTAGE = 5.0V/div

CAPACITOR VOLTAGE = 1.0V/div

L

R = R = 4.8 k , C = 0.1 F , R = 1.0k

AB

Figure 5

ASTABLE OPERATION

When the circuit is connected as shown in

figure 4 , it triggers itself and free runs as a

multivibrator. The external capacitor charges

Thus the duty cycle may be precisely set by the ra-

tio of these two resistors.

In the astable mode of operation, C charges and

triggered mode, the charge and discharge times

and therefore frequency, are independent of the

supply voltage.

Figure 5 shows actual waveforms generated in this

mode of operation.

The charge time (output HIGH) is given by :

and the discharge time (output LOW) by :

Thus the total period T is given by :

The frequency of oscillation is then :

f

TR

R ) C

B

==

+

1144

2

.

(

A

The duty cycle is given by : D

R

RR

=

+

B

AB

2