TLC555-Q1 Datasheet, PDF (13/25 Pages) Texas Instruments – LinCMOS™ TIMER

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9 Application and Implementation
TLC555-Q1
SLFS078B – OCTOBER 2006 – REVISED OCTOBER 2015
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 TLC555-Q1 timer device uses resistor and capacitor charging delay to provide a programmable time delay
or operating frequency. The following section presents a simplified discussion of the design process.
9.2 Typical Applications
9.2.1 Missing-Pulse Detector
The circuit shown in Figure 12 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 13.
V_DD (5 V to 15 V)
Input
4
RESET
2 _TRIG
8
R_L
V_DD
3
OUT
DISCH ⁷
5
CONT
0.01 mF
6
THRES
GND
1
R_A
Output
C
A5T3644
Figure 12. 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)
remains discharged.
9.2.1.2 Detailed Design Procedure
Choose R_A and C so that R_A× C > [maximum normal input high time]. R_L improves V_OH, but it is not required for
TTL compatibility.
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