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ISO1050: TXD Dominant Time-Out

Francis Jiang
Expert 4540 points

Part Number: ISO1050

Tool/software:

Hi Team,

Customer use ISO1050 in always Dominant mode or Recessive mode, and in always Dominant mode, it will occur TXD Dominant Time-Out issue. Do you have any suggestion to avoid this issue? Thanks in advance.

BRs,

Francis

  • 0
    TI__Mastermind 34580 points

    Hello Francis, 

    The ISO1050 inegrates a dominant timout (DTO) feature as you have noticed. CAN is a bus protocol and other nodes will not be able to transmit if the CAN transiever is driving dominant for long periods of time. Many CAN transievers (like ISO1050) integrate a DTO feature to realease the CAN bus to a rescessive state if TXD is being contiinoutly asserted. This allows for a more robust performance of the CAN bus as a whole. 

    The ISO1050 will transition to the recessive state is TXD is driven low longer than the spec: tTXD_DTO (Dominant time out) = 1.2ms (min). 

    In order to avoid this: 

    1. Calculate the minimum data rate to be greater than section 8.3.3.1 TXD Dominant Time-Out (DTO). 
    2. Ensure that a given data packet does not send succesive low bits that could trigger DTO
    3. Ensure the MCU does not drive TXD low when idle or use a pull-up resistor to VCC1 if TXD will be High-Z 

    Best,
    Andrew