Datasheet NA555, NE555, SA555, SE555 (Texas Instruments) - 10

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NA555, NE555, SA555, SE555
SLFS022I – SEPTEMBER 1973 – REVISED SEPTEMBER 2014
www.ti.com Feature Description (continued) VCC (5 V to 15 V) 5 R
Î
8 A
Î
CONT VCC RL 4
Î
RESET 7 DISCH 3 OUT Output 6 THRES 2 Input TRIG GND 1
Pin numbers shown are for the D, JG, P, PS, and PW packages.
Figure 9. Circuit for Monostable Operation
Monostable operation is initiated when TRIG voltage falls below the trigger threshold. Once initiated, the sequence ends only if TRIG is high for at least 10 µs before the end of the timing interval. When the trigger is grounded, the comparator storage time can be as long as 10 µs, which limits the minimum monostable pulse width to 10 µs. Because of the threshold level and saturation voltage of Q1, the output pulse duration is approximately tw = 1.1RAC. Figure 11 is a plot of the time constant for various values of RA and C. The threshold levels and charge rates both are directly proportional to the supply voltage, VCC. The timing interval is, therefore, independent of the supply voltage, so long as the supply voltage is constant during the time interval. Applying a negative-going trigger pulse simultaneously to RESET and TRIG during the timing interval discharges C and reinitiates the cycle, commencing on the positive edge of the reset pulse. The output is held low as long ÏÏÏÏÏ as the reset pulse is low. To prevent false triggering, when RESET is not used, it should be connected to VCC.
10
ÏÏÏÏÏ
RA = 9.1 k
Ω
RA = 10 M
Ω ÏÏÏÏÏ
CL = 0.01
µ
F RL = 1 k
Ω ÏÏÏÏÏ
See Figure 9 1 RA = 1 M
Ω ÏÏÏÏÏ
10−1 Input Voltage 10−2 10−3 oltage − 2 V/div V RA = 100 k
Ω
Output Voltage − Output Pulse Duration − s RA = 10 k
Ω
t w 10−4
ÏÏÏÏÏÏ
R
ÏÏÏÏÏÏ
A = 1 k
Ω
10−5
ÏÏÏÏÏÏ
Capacitor Voltage 0.001 0.01 0.1 1 10 100
ÏÏÏÏÏÏ
Time − 0.1 ms/div C − Capacitance −
µ
F Figure 10. Typical Monostable Waveforms Figure 11. Output Pulse Duration vs Capacitance
10 Submit Documentation Feedback Copyright © 1973–2014, Texas Instruments Incorporated Product Folder Links: NA555 NE555 SA555 SE555 Document Outline 1 Features 2 Applications 3 Description 4 Simplified Schematic Table of Contents 5 Revision History 6 Pin Configuration and Functions 7 Specifications 7.1 Absolute Maximum Ratings 7.2 Handling Ratings 7.3 Recommended Operating Conditions 7.4 Electrical Characteristics 7.5 Operating Characteristics 7.6 Typical Characteristics 8 Detailed Description 8.1 Overview 8.2 Functional Block Diagram 8.3 Feature Description 8.3.1 Mono-stable Operation 8.3.2 A-stable Operation 8.3.3 Frequency Divider 8.4 Device Functional Modes 9 Applications and Implementation 9.1 Application Information 9.2 Typical Applications 9.2.1 Missing-Pulse Detector 9.2.1.1 Design Requirements 9.2.1.2 Detailed Design Procedure 9.2.1.3 Application Curves 9.2.2 Pulse-Width Modulation 9.2.2.1 Design Requirements 9.2.2.2 Detailed Design Procedure 9.2.2.3 Application Curves 9.2.3 Pulse-Position Modulation 9.2.3.1 Design Requirements 9.2.3.2 Detailed Design Procedure 9.2.3.3 Application Curves 9.2.4 Sequential Timer 9.2.4.1 Design Requirements 9.2.4.2 Detailed Design Procedure 9.2.4.3 Application Curves 10 Power Supply Recommendations 11 Device and Documentation Support 11.1 Related Links 11.2 Trademarks 11.3 Electrostatic Discharge Caution 11.4 Glossary 12 Mechanical, Packaging, and Orderable Information