TS555

Application information

13/20

4.2

Astable operation

When the circuit is connected as shown in Figure 6 (pins 2 and 6 connected) it triggers itself

these two resistors.

As in the triggered mode, the charge and discharge times, and therefore frequency, are

independent of the supply voltage.

Figure 6.

Application schematic

Figure 7 shows actual waveforms generated in this mode of operation.

The charge time (output HIGH) is given by:

The discharge time (output LOW) by:

Thus the total period T is given by:

The frequency of oscillation is then:

The duty cycle is given by:

Figure 7.

Timing diagram

Reset

Out

3

4

8

7

5

1

TS555

R

C

2

6

R

A

B

Control

Voltage

0.01 F

μ

f =

1

T

--- =

1.44

(RA

2RB

)C

+

--------------------------------------

D =

RB

RA

2RB

+

---------------------------

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