Datasheet LM556 (Texas Instruments) - 10

link to page 10 link to page 10 link to page 11 link to page 11
LM556
SNAS549A – MARCH 2000 – REVISED OCTOBER 2015
www.ti.com 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 LM556 timer can be used in various configurations. A typical application for the LM556 timer in astable mode is to drive an audio device (such as a beeper) to provide a pulsed sound. This simple application can be modified to fit any application requirement.
8.2 Typical Application
R2A R 4 1 1A 2 5 LM556 Vout 6 3 10 13 0.01 µF Vin 0.01 µF 12 9 R1B 8 11 14 7 10 µF 0.01 µF 100 µF R2B
Figure 13. Typical Application 8.2.1 Design Requirements
The main design requirements for this application require setting one of the timers (Timer A in this case) to the same resonant frequency as the piezo transducer which can be set by choosing R1A, R2A, and CA with Equation 1: 1.44 fo = R R C (( A + 2 A 1 2 ) (1) The other design choice is to decide how often and long to produce the bleeping sound. This can be set by choosing R1B and R2B of Timer B (acts as the reset button for Timer A) with Equation 2: R2B D = R B +R 1 2B (2) Other useful design equations like Equation 3 and Equation 4 are given below where th represents the time it takes to charge the capacitor of each individual timer and tl represents the time it takes to discharge the capacitor. 10 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM556 Document Outline 1 Features 2 Applications 3 Description Table of Contents 4 Revision History 5 Pin Configuration and Functions 6 Specifications 6.1 Absolute Maximum Ratings 6.2 ESD Ratings 6.3 Recommended Operating Conditions 6.4 Thermal Information 6.5 Electrical Characteristics 6.6 Typical Characteristics 7 Detailed Description 7.1 Overview 7.2 Functional Block Diagram 7.3 Feature Description 7.3.1 Operating Characteristics 7.3.2 Timing from Microseconds Through Hours 7.4 Device Functional Modes 7.4.1 Monostable Mode 7.4.2 Astable (Free-Running) Mode 8 Application and Implementation 8.1 Application Information 8.2 Typical Application 8.2.1 Design Requirements 8.2.2 Detailed Design Procedure 8.2.3 Application Curve 9 Power Supply Recommendations 10 Layout 10.1 Layout Guidelines 10.2 Layout Example 11 Device and Documentation Support 11.1 Documentation Support 11.1.1 Related Documentation 11.2 Community Resources 11.3 Trademarks 11.4 Electrostatic Discharge Caution 11.5 Glossary 12 Mechanical, Packaging, and Orderable Information