S

VCC

RESET

VCC

OUT

DISCH

GND

CONT

TRIG

4

8

3

7

6

1

5

2

THRES

RC

CC

0.01

CC = 14.7 µF

RC = 100 kΩ

Output C

RESET

VCC

OUT

DISCH

GND

CONT

TRIG

4

8

3

7

6

1

5

2

THRES

RB

33 k

Ω

0.001

0.01

µF

CB = 4.7 µF

RB = 100 kΩ

Output B

Output A

RA = 100 kΩ

CA = 10 µF

µF

0.01

µF

0.001

33 k

Ω

RA

THRES

2

5

1

6

7

3

8

4

TRIG

CONT

GND

DISCH

OUT

VCC

RESET

µF

µF

CB

CA

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

NOTE A: S closes momentarily at t = 0.

RA = 3 kΩ

RB = 500 Ω

RL = 1 kΩ

See Figure 20

Capacitor Voltage

Output Voltage

Modulation Input Voltage

Time − 0.1 ms/div

NA555, NE555, SA555, SE555

www.ti.com

SLFS022I – SEPTEMBER 1973 – REVISED SEPTEMBER 2014

Typical Applications (continued)

9.2.3.3 Application Curves

Figure 21. Pulse-Position-Modulation Waveforms

9.2.4 Sequential Timer

Many applications, such as computers, require signals for initializing conditions during start-up. Other

applications, such as test equipment, require activation of test signals in sequence. These timing circuits can be

connected to provide such sequential control. The timers can be used in various combinations of astable or

monostable circuit connections, with or without modulation, for extremely flexible waveform control. Figure 22

shows a sequencer circuit with possible applications in many systems, and Figure 23 shows the output

waveforms.

Figure 22. Sequential Timer Circuit

Copyright © 1973–2014, Texas Instruments Incorporated

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