SCLS420H June   1998  – January 2025 SN54AHCT123A , SN74AHCT123A

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Description
  4. 3 Pin Configuration and Functions
  5. 4 Specifications
    1. 4.1 Absolute Maximum Ratings
    2. 4.2 ESD Ratings
    3. 4.3 Recommended Operating Conditions
    4. 4.4 Thermal Information
    5. 4.5 Electrical Characteristics
    6. 4.6 Timing Requirements
    7. 4.7 Switching Characteristics
    8. 4.8 Operating Characteristics
    9. 4.9 Input/Output Timing Diagram
  6. 5 Parameter Measurement Information
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 CMOS Schmitt-Trigger Inputs
      2. 6.3.2 TTL-Compatible CMOS Inputs
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Caution in Use
      2. 7.1.2 Power-down Considerations
      3. 7.1.3 Output Pulse Duration
      4. 7.1.4 Retriggering Data
    2. 7.2 Power Supply Recommendations
    3. 7.3 Layout
      1. 7.3.1 Layout Guidelines
      2. 7.3.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.1.3 Output Pulse Duration

The output pulse duration, tw, is determined primarily by the values of the external capacitance (CT) and timing resistance (RT). The timing components are connected as shown in Figure 7-1.

SN54AHCT123A SN74AHCT123A Timing-Component Connections Figure 7-1 Timing-Component Connections

The pulse duration is given by:

tw = K × RT × CT (1)

if CT is ≥ 1000 pF, K = 1.0 or

if CT is < 1000 pF, K can be determined from Figure 7-4

where:

tw = pulse duration in ns

RT = external timing resistance in kΩ

CT = external capacitance in pF

K = multiplier factor

Equation 1 and Figure 7-2 can be used to determine values for pulse duration, external resistance, and external capacitance.