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ISO1050: ISO1050 questions in low data rate CAN

Part Number: ISO1050

Customer reported there is a problem in ISO1050 if CAN bus data rate is very low(~10Kbps). there is a "Dominant time-out" limit spec in section 6.9 of datasheet. 

questions; Does ISO1050 support 10Kbps CAN? is Dominant time-out limitation in this ultra low data rate application in IOS1050?

  • Hi Peter,

    Yes the dominant time out does limit the minimum data rate possible. See the note after section 6.9 Switching Characteristis: Driver at the bottom of page 8 of the ISO1050 datasheet.

    "The TXD dominant time out (tTXD_DTO) disables the driver of the transceiver once the TXD has been dominant longer than (tTXD_DTO) which releases the bus lines to recessive preventing a local failure from locking the bus dominant. The driver may only transmit dominant again after TXD has been returned HIGH (recessive). While this protects the bus from local faults locking the bus dominant it limits the minimum data rate possible. The CAN protocol allows a maximum of eleven successive dominant bits (on TXD) for the worst case where five successive dominant bits are followed immediately by an error frame. This along with the (tTXD_DTO) minimum limits the minimum bit rate. The minimum bit rate may be calculated by: Minimum Bit Rate = 11/ (tTXD_DTO) = 11 bits / 300 µs = 37 kbps."

    In answer to your question, no the ISO1050 does not support 10Kbps CAN.

    Thanks for posting this question and best regards,

    Dan