SCHS346C April   2003  – October 2024 CD74AC174

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Application
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Electrical Characteristics
    6. 5.6  Timing Requirements, VCC = 1.5 V
    7. 5.7  Timing Requirements, VCC = 3.3 V ± 0.3 V
    8. 5.8  Timing Requirements, VCC = 5 V ± 0.5 V
    9. 5.9  Switching Characteristics, VCC = 1.5 V
    10. 5.10 Switching Characteristics, VCC = 3.3 V ± 0.3 V
    11. 5.11 Switching Characteristics, VCC = 5 V ± 0.5 V
    12. 5.12 Operating Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Power Supply Recommendations
    2. 8.2 Layout
      1. 8.2.1 Layout Guidelines
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support (Analog)
      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

8.2.1 Layout Guidelines

When using multiple bit logic devices inputs should not ever float.

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 or only 3 of the 4 buffer gates are used. Such input pins should not be left unconnected because the undefined voltages at the outside connections result in undefined operational states. Specified below are the rules that must be observed under all circumstances. All unused inputs of digital logic devices must be connected to a high or low bias to prevent them from floating. The logic level that should be applied to any particular unused input depends on the function of the device. Generally they will be tied to GND or VCC whichever make more sense or is more convenient. It is generally okay to float outputs unless the part is a transceiver. If the transceiver has an output enable pin it will disable the outputs section of the part when asserted. This does not disable the input section of the IOs so they cannot float when disabled.