SLLS872J January   2008  – March 2023 SN65HVD1785 , SN65HVD1786 , SN65HVD1787 , SN65HVD1791 , SN65HVD1792 , SN65HVD1793

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Product Selection Guide
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings (1)
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Thermal Considerations
    7. 7.7 Switching Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Hot-Plugging
      2. 9.3.2 Receiver Failsafe
      3. 9.3.3 70-V Fault-Protection
      4. 9.3.4 Additional Options
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
        1. 10.2.1.1 Data Rate and Bus Length
        2. 10.2.1.2 Stub Length
        3. 10.2.1.3 Receiver Failsafe
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curve
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Support Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.2.1.3 Receiver Failsafe

The differential receiver of the SN75HVD17xx family is failsafe to invalid bus states caused by:

  • Open bus conditions, such as a disconnected connector
  • Shorted bus conditions, such as cable damage shorting the twisted-pair together
  • Idle bus conditions that occur when no driver on the bus is actively driving
n any of these cases, the differential receiver will output a failsafe logic high state so that the output of the receiver is not indeterminate.

Receiver failsafe is accomplished by offsetting the receiver thresholds such that the “input indeterminate” range does not include zero volts differential. In order to comply with the RS-422 and RS-485 standards, the receiver output must output a high when the differential input VID is more positive than +200 mV, and must output a low when VID is more negative than -200 mV. The receiver parameters which determine the failsafe performance are VIT(+) and VIT(-). As shown in the Electrical Characteristics table, differential signals more negative than -200 mV will always cause a low receiver output, and differential signals more positive than +200 mV will always cause a high receiver output.

When the differential input signal is close to zero, it is still above the maximum VIT(+) threshold of -10 mV, and the receiver output will be high.