SLLSF19 December   2017 TCAN4420

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Functional Block Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 ESD Ratings Specifications
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Power Supply Characteristics
    7. 6.7 AC and DC Electrical Characteristics
    8. 6.8 Timing Requirements
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagrams
    3. 8.3 Feature Description
      1. 8.3.1 TXD Dominant Time Out (DTO)
      2. 8.3.2 CAN Bus Short Circuit Current Limiting
      3. 8.3.3 Thermal Shutdown
      4. 8.3.4 Under Voltage Lockout (UVLO) and Unpowered Device
        1. 8.3.4.1 VIO Supply PIN
    4. 8.4 Device Functional Modes
      1. 8.4.1 Polarity Configuration
      2. 8.4.2 Normal Polarity Mode
      3. 8.4.3 Reverse Polarity Mode
      4. 8.4.4 Driver and Receiver Function
      5. 8.4.5 Floating Terminals
  9. 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 Bus Loading, Length and Number of Nodes
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 CAN Termination
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Device Nomenclature
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.3.2 CAN Bus Short Circuit Current Limiting

The TCAN4420 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). During CAN communication the bus switches between dominant and recessive states, thus the short circuit current may 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 should be 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 inter frame space. These ensure 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 may be calculated using Equation 1.

Equation 1. 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.

NOTE

The short circuit current and possible fault cases of the network should be taken into consideration when sizing the power ratings of the termination resistance, other network components, and the power supply used to generate VCC.