SCAS521H August   1995  – June 2025 SN54AC74 , SN54AC74-SP , SN74AC74

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 Recommended Operating Conditions
    3. 5.3 Thermal Information
    4. 5.4 Electrical Characteristics
    5. 5.5 Timing Requirements, VCC = 3.3 V ± 0.3 V
    6. 5.6 Timing Requirements, VCC = 5 V ± 0.5 V
    7. 5.7 Switching Characteristics, VCC = 3.3 V ± 0.3 V
    8. 5.8 Switching Characteristics, VCC = 5 V ± 0.5 V
    9. 5.9 Operating Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Balanced CMOS Push-Pull Outputs
      2. 7.3.2 Latching Logic
      3. 7.3.3 Standard CMOS Inputs
      4. 7.3.4 Clamp Diode Structure
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
        1. 8.2.1.1 Power Considerations
        2. 8.2.1.2 Input Considerations
        3. 8.2.1.3 Output Considerations
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.1 Application Information

Toggle switches are typically large, mechanically complex and relatively expensive. It is desirable to use a momentary switch instead because they are small, mechanically simple and low cost. Some systems require a toggle switch's functionality but are space or cost constrained and must use a momentary switch instead.

If the data input (D) of the D-type flip-flop is tied to the inverted output (Q), then each clock pulse will cause the value at the output (Q) to toggle. The momentary switch can be debounced and connected through a Schmitt-trigger buffer to the clock input (CLK) to toggle the output.

This application also utilizes a power-on reset circuit so that the output always starts in the LOW state when power is applied.