L

B

H

A

B

t

R

Low-to-high ratio

t

R

R

=

=

+

H

B

H

L

A

B

t

R

Output waveform duty cycle

1

t

t

R

2R

=

= -

+

+

L

B

H

L

A

B

t

R

Output driver duty cycle

t

t

R

2R

=

=

+

+

(

)

A

B

1.44

frequency

R

2R

C

»

+

(

)

H

L

A

B

period

t

t

0.693 R

2R

C

=

+

=

+

( )

L

B

t

0.693 R

C

=

(

)

H

A

B

t

0.693 R

R

C

=

+

GND

OUT

CONT

RESET

DISCH

THRES

TRIG

C

Output

0.01

(5 V to 15 V)

(see Note A)

NOTE A: Decoupling CONT voltage to ground with a capacitor can

improve operation. This should be evaluated for individual

applications.

Open

5

8

4

7

6

2

3

1

Pin numbers shown are for the D, JG, P, PS, and PW packages.

Time − 0.5 ms/div

t

H

Capacitor Voltage

Output Voltage

See Figure 12

C = 0.15

µF

NA555, NE555, SA555, SE555

www.ti.com

SLFS022I – SEPTEMBER 1973 – REVISED SEPTEMBER 2014

Feature Description (continued)

8.3.2 A-stable Operation

the threshold input causes the timer to self-trigger and run as a multi-vibrator. The capacitor C charges through

This astable connection results in capacitor C charging and discharging between the threshold-voltage level (

≈

times (and, therefore, the frequency and duty cycle) are independent of the supply voltage.

Figure 12. Circuit for Astable Operation

Figure 13. Typical Astable Waveforms

(1)

(2)

Other useful relationships are shown below:

(3)

(4)

(5)

(6)

(7)

Copyright © 1973–2014, Texas Instruments Incorporated

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