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TCAN1042H: Fault Conditions and Current Draw

Kurt Schmidt
Genius 11125 points
Part Number: TCAN1042H

Can you help me with this question from my customer: 

"I am looking at TCAN1042 as part of the exercise to make sure the system power supply can handle bus fault current.  From TCAN1042 datasheet, the published fault current is 180mA when CANH is biased at -12V.  I wonder how this type of fault could occur in real applications.  In addition, I wonder what the maximum transceiver current draw will be when either CAN_H or CAN_L is shorted to return or VCC?"

 

  • 0
    TI__Guru 62920 points
    Kurt,

    It does seem like kind of a far-fetched condition to me. If you had CANH shorted to a battery line and then the battery connected in reverse, you could end up with a negative voltage on CANH with respect to the GND pin. In order for the transceiver output to be dominant, though, you would need to have the transceiver/rest of system properly powered while this is all occurring (which may be difficult if the battery is connected in reverse). Maybe this could occur during a jump start if the user made just the right sequence of mistakes?

    When shorting CANH to VCC (or greater) or CANL to ground (or lower), no significant currents will flow. This is because there is a blocking diode on the CANH/CANL drivers to prevent higher/lower voltages from coupling through to the power supply.

    When shorting CANH to ground or CANL to VCC, the output current flowing into or out of the shorted pin is limited to 100 mA per the IOS(SS_DOM) spec. For the case of the CANH short, this additional current would flow through VCC; for the case of the CANL short, this current would flow through ground.

    Please just let us know if you have any further questions.

    Regards,
    Max