S

RESET

OUT

DISCH

GND

CONT

TRIG

4

8

3

7

6

1

5

2

THRES

0.01

Output C

RESET

OUT

DISCH

GND

CONT

TRIG

4

8

3

7

6

1

5

2

THRES

33 k

Ω

0.001

0.01

µF

Output B

Output A

µF

0.01

µF

0.001

33 k

Ω

RA

THRES

2

5

1

6

7

3

8

4

TRIG

CONT

GND

DISCH

OUT

RESET

µF

µF

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

NOTE A: S closes momentarily at t = 0.

t − Time − 1 s/div

See Figure 22

Output A

Output B

Output C

t = 0

NA555, NE555, SA555, SE555

www.ti.com

SLFS022H – SEPTEMBER 1973 – REVISED JUNE 2010

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

Figure 23. Sequential Timer Waveforms

Copyright © 1973–2010, Texas Instruments Incorporated

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