DISCH

OUT

RESET

2N3906

C

THRES

GND

CONT

TRIG

Input

0.01 F

P

Output

4

8

3

7

6

2

5

1

20

TLC555

SLFS043I – SEPTEMBER 1983 – REVISED JULY 2019

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Copyright © 1983–2019, Texas Instruments Incorporated

8 Application 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.

8.1 Application Information

The TLC555 timer device uses resistor and capacitor charging delay to provide a programmable time delay or

operating frequency. The Typical Applications section presents a simplified discussion of the design process.

Reset mode forces output and discharge low and provides a small reduction in supply current.

8.2 Typical Applications

8.2.1 Missing-Pulse Detector

The circuit shown in Figure 18 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 19.

Figure 18. Circuit for Missing-Pulse Detector

8.2.1.1 Design Requirements

Input fault (missing pulses) must be input high. An input stuck low cannot be detected because the timing

capacitor (C) remains discharged.

8.2.1.2 Detailed Design Procedure