ZHCSO46 December   2021 TCAN1057AEV-Q1

PRODUCTION DATA  

  1. 特性
  2. 应用
  3. 说明
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 ESD Ratings Table — IEC Specifications
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Characteristics
    6. 6.6 Supply Characteristics
    7. 6.7 Dissipation Ratings
    8. 6.8 Electrical Characteristics
    9. 6.9 Switching Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Pin Description
        1. 8.3.1.1 TXD
        2. 8.3.1.2 GND
        3. 8.3.1.3 VCC
        4. 8.3.1.4 RXD
        5. 8.3.1.5 VIO
        6. 8.3.1.6 CANH and CANL
        7. 8.3.1.7 S (Silent)
      2. 8.3.2 CAN Bus States
      3. 8.3.3 TXD Dominant Timeout (DTO)
      4. 8.3.4 CAN Bus Short-Circuit Current Limiting
      5. 8.3.5 Thermal Shutdown (TSD)
      6. 8.3.6 Undervoltage Lockout
      7. 8.3.7 Unpowered Device
      8. 8.3.8 Floating Pins
    4. 8.4 Device Functional Modes
      1. 8.4.1 Operating Modes
      2. 8.4.2 Normal Mode
      3. 8.4.3 Silent Mode
      4. 8.4.4 Driver and Receiver Function
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 CAN Termination
      2. 9.2.2 Detailed Design Procedures
        1. 9.2.2.1 Bus Loading, Length and Number of Nodes
      3. 9.2.3 Application Curves
      4. 9.2.4 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 Documentation Support
    2. 12.2 接收文档更新通知
    3. 12.3 支持资源
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 术语表
  13. 13Mechanical, Packaging, and Orderable Information

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订购信息

CAN Bus Short-Circuit Current Limiting

The device has several protection features that limit the short-circuit current when a CAN bus line is shorted. These features include CAN driver current limiting in the dominant and recessive states and TXD dominant state timeout which prevents permanently having the higher short-circuit current of a dominant state in case of a system fault. During CAN communication the bus switches between the dominant and recessive states, therefore the short-circuit current is viewed as either the current during each bus state or as a DC average current. When selecting termination resistors or a common mode choke for the CAN design, the IOS(AVG) should be used, which is the average current rating. The percentage dominant is limited by the TXD DTO and the CAN protocol which has forced state changes and recessive bits due to bit stuffing, control fields, and interframe space. These features ensure there is a minimum amount of recessive time on the bus even if the data field contains a high percentage of dominant bits.

The average 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 may be calculated using Equation 2.

Equation 2. IOS(AVG) = % Transmit x [(% REC_Bits x IOS(SS)_REC) + (% DOM_Bits x IOS(SS)_DOM)] + [% Receive x 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

This short-circuit current and the possible fault cases of the network should be taken into consideration when sizing the power supply used to generate the transceivers VCC supply.