DISCH

OUT

RESET

A5T3644

C

THRES

GND

CONT

TRIG

Input

0.01

Output

4

8

3

7

6

2

5

1

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

NA555, NE555, SA555, SE555

www.ti.com

SLFS022I – SEPTEMBER 1973 – REVISED SEPTEMBER 2014

9 Applications and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The xx555 timer devices use resistor and capacitor charging delay to provide a programmable time delay or

operating frequency. This section presents a simplified discussion of the design process.

9.2 Typical Applications

9.2.1 Missing-Pulse Detector

The circuit shown in Figure 16 can be used to detect a missing pulse or abnormally long spacing between

consecutive pulses in a train of pulses. The timing interval of the monostable circuit is re-triggered continuously

by the input pulse train as long as the pulse spacing is less than the timing interval. A longer pulse spacing,

missing pulse, or terminated pulse train permits the timing interval to be completed, thereby generating an output

pulse as shown in Figure 17.

Figure 16. Circuit for Missing-Pulse Detector

9.2.1.1 Design Requirements

Input fault (missing pulses) must be input high. Input stuck low will not be detected because timing capacitor "C"

will remain discharged.

9.2.1.2 Detailed Design Procedure

TTL compatibility.

Copyright © 1973–2014, Texas Instruments Incorporated

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Product Folder Links: NA555 NE555 SA555 SE555