SDLS144D April   1985  – October 2016 SN54LS240 , SN54LS241 , SN54LS244 , SN54S240 , SN54S241 , SN54S244 , SN74LS240 , SN74LS241 , SN74LS244 , SN74S240 , SN74S241 , SN74S244

 

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics - SNx4LS24x
    6. 6.6 Electrical Characteristics - SNx4S24x
    7. 6.7 Switching Characteristics - SNx4LS24x
    8. 6.8 Switching Characteristics - SNx4S24x
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 SN54LS24x and SN74LS24x Devices
    2. 7.2 SN54S24x and SN74S24x Devices
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagrams
    3. 8.3 Feature Description
      1. 8.3.1 3-State Outputs
      2. 8.3.2 PNP Inputs
      3. 8.3.3 Hysteresis on Bus Inputs
    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
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
    3. 9.3 System Examples
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Related Links
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resource
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

11 Layout

11.1 Layout Guidelines

When using multiple bit logic devices, inputs must not be left floating. In many applications, some channels of the SNx4LS24x, SNx4S24x are unused, and thus must be terminated properly. Because each transceiver channel pin can be either an input or an output, they must be treated as both when being terminated. Ground or VCC (whichever is more convenient) can be used to terminate unused inputs; however, each unused channel should be terminated to the same logic level on both the A and Y side. For example, in Figure 27 unused channels are terminated correctly with both sides connected to the same voltage, while channel 8 is terminated incorrectly with each side being tied to a different voltage. The G input is also unused in this example, and is terminated directly to ground to permanently enable all outputs.

11.2 Layout Example

SN54LS240 SN54LS241 SN54LS244 SN54S240 SN54S241 SN54S244 SN74LS240 SN74LS241 SN74LS244 SN74S240 SN74S241 SN74S244 layout_scls749.gif Figure 27. Example Demonstrating How to Terminate Unused Inputs and Channels of a Transceiver