SLLSEV0F November   2017  – November 2023 TCAN1043-Q1 , TCAN1043G-Q1 , TCAN1043H-Q1 , TCAN1043HG-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 ESD Ratings IEC Specification
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Dissipation Ratings
    7. 6.7 Electrical Characteristics
    8. 6.8 Switching Characteristics
    9. 6.9 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Internal and External Indicator Flags (nFAULT and RXD)
      2. 8.3.2 Power-Up Flag (PWRON)
      3. 8.3.3 Wake-Up Request Flag (WAKERQ)
      4. 8.3.4 Wake-Up Source Recognition Flag (WAKESR)
      5. 8.3.5 Undervoltage Fault Flags
        1. 8.3.5.1 Undervoltage on VCC Fault
        2. 8.3.5.2 Undervoltage on VIO Fault
        3. 8.3.5.3 Undervoltage on VSUP Fault
      6. 8.3.6 CAN Bus Failure Fault Flag
      7. 8.3.7 Local Faults
        1. 8.3.7.1 TXD Dominant Timeout (TXD DTO)
        2. 8.3.7.2 TXD Shorted to RXD Fault
        3. 8.3.7.3 CAN Bus Dominant Fault
        4. 8.3.7.4 Thermal Shutdown (TSD)
        5. 8.3.7.5 RXD Recessive Fault
        6. 8.3.7.6 Undervoltage Lockout (UVLO)
        7. 8.3.7.7 Unpowered Device
        8. 8.3.7.8 Floating Terminals
        9. 8.3.7.9 CAN Bus Short Circuit Current Limiting
    4. 8.4 Device Functional Modes
      1. 8.4.1 CAN Bus States
      2. 8.4.2 Normal Mode
      3. 8.4.3 Silent Mode
      4. 8.4.4 Standby Mode
      5. 8.4.5 Go-to-Sleep Mode
      6. 8.4.6 Sleep Mode with Remote Wake and Local Wake Up Requests
        1. 8.4.6.1 Remote Wake Request via Wake Up Pattern (WUP)
        2. 8.4.6.2 Local Wake Up (LWU) via WAKE Input Terminal
      7. 8.4.7 Driver and Receiver Function Tables
      8. 8.4.8 Digital Inputs and Outputs
      9. 8.4.9 INH (Inhibit) Output
  10. 9 Application Information Disclaimer
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 Bus Loading, Length and Number of Nodes
      2. 9.2.2 Detailed Design Procedures
        1. 9.2.2.1 CAN Termination
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout
        1. 9.4.1.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

8.3.7.9 CAN Bus Short Circuit Current Limiting

The TCAN1043xx-Q1 has several protection features that limit the short circuit current when a CAN bus line is shorted. These include CAN driver current limiting (dominant and recessive). The device has TXD dominant time out which prevents permanently having the higher short circuit current of dominant state in case of a system fault. During CAN communication the bus switches between dominant and recessive states, thus the short circuit current can be viewed either as the current during each bus state or as a DC average current. For system current and power considerations in the termination resistors and common mode choke ratings, the average short circuit current is typically used. The percentage dominant is limited by the TXD dominant time out and CAN protocol which has forced state changes and recessive bits such as bit stuffing, control fields, and interframe space. These make sure there is a minimum recessive amount of time on the bus even if the data field contains a high percentage of dominant bits.

The short circuit current of the bus depends on the ratio of recessive to dominant bits and their respective short circuit currents. The average short circuit current can be calculated with Equation 1.

Equation 1. IOS(AVG) = %Transmit × [(%REC_Bits × IOS(SS)_REC) + (%DOM_Bits × IOS(SS)_DOM)] + [%Receive × IOS(SS)_REC]

Where:

  • IOS(AVG) is the average short circuit current
  • %Transmit is the percentage the node is transmitting CAN messages
  • %Receive is the percentage the node is receiving CAN messages
  • %REC_Bits is the percentage of recessive bits in the transmitted CAN messages
  • %DOM_Bits is the percentage of dominant bits in the transmitted CAN messages
  • IOS(SS)_REC is the recessive steady state short circuit current
  • IOS(SS)_DOM is the dominant steady state short circuit current

Note:

The short circuit current and possible fault cases of the network can be taken into consideration when sizing the power ratings of the termination resistance and other network components.