SCLS087F December   1982  – June 2021 SN54HC21 , SN74HC21

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Recommended Operating Conditions
    3. 6.3 Thermal Information
    4. 6.4 Electrical Characteristics - 74
    5. 6.5 Electrical Characteristics - 54
    6. 6.6 Switching Characteristics - 74
    7. 6.7 Switching Characteristics - 54
    8. 6.8 Operating Characteristics
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Balanced CMOS Push-Pull Outputs
      2. 8.3.2 Standard CMOS Inputs
      3. 8.3.3 Clamp Diode Structure
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 Power Considerations
        2. 9.2.1.2 Input Considerations
        3. 9.2.1.3 Output Considerations
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • J|14
  • FK|20
Thermal pad, mechanical data (Package|Pins)
Orderable Information

11.1 Layout Guidelines

When using multiple-input and multiple-channel logic devices inputs must not ever be left floating. In many cases, functions or parts of functions of digital logic devices are unused; for example, when only two inputs of a triple-input AND gate are used. Such unused input pins must not be left unconnected because the undefined voltages at the outside connections result in undefined operational states. All unused inputs of digital logic devices must be connected to a logic high or logic low voltage, as defined by the input voltage specifications, to prevent them from floating. The logic level that must be applied to any particular unused input depends on the function of the device. Generally, the inputs are tied to GND or VCC, whichever makes more sense for the logic function or is more convenient.