SLLSF78B December   2020  – October 2021 THVD1400 , THVD1420

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Revision History
  4. 4 Pin Configuration and Functions
  5. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  ESD Ratings [IEC]
    4. 5.4  Recommended Operating Conditions
    5. 5.5  Thermal Information
    6. 5.6  Power Dissipation Characteristics
    7. 5.7  Electrical Characteristics
    8. 5.8  Switching Characteristics (THVD1400)
    9. 5.9  Switching Characteristics (THVD1420)
    10. 5.10 Typical Characteristics
  6. 6 Parameter Measurement Information
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
    4. 7.4 Device Functional Modes
  8. 8 Application Information Disclaimer
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
        1. 8.2.1.1 Data Rate and Bus Length
        2. 8.2.1.2 Stub Length
        3. 8.2.1.3 Bus Loading
        4. 8.2.1.4 Receiver Failsafe
        5. 8.2.1.5 Transient Protection
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.1.4 Receiver Failsafe

The differential receivers of the THVD1400 are failsafe to invalid bus states caused by the following:

  • 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

In any of these cases, the differential receiver outputs 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. 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+, VIT–, and VHYS (the separation between VIT+ and VIT–). As shown in the Table 7-2, differential signals more negative than –200 mV always causes a low receiver output, and differential signals more positive than 200 mV always causes a high receiver output.

When the differential input signal is close to zero, it is still above the VIT+ threshold, and the receiver output is high. Only when the differential input is more than VHYS below VIT+ does the receiver output transition to a low state. Therefore, the noise immunity of the receiver inputs during a bus fault conditions includes the receiver hysteresis value, VHYS, as well as the value of VIT+.