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ISO1050 bus fault protection

Shing Lee
Intellectual 545 points
Other Parts Discussed in Thread: ISO1050

The ISO1050 datasheet describes a bus-fault protection of -27V to 40V.  Are these CAN_H and CAN_L over-voltage protection clamping voltage?  I would like to determine what would happen if CAN_H or CAN_L is shorted to say 30V, will the VCC2 gets pulled to 30V as well.  The equivalent I/O schematics diagram suggests that VCC2 is protected (CAN_H line) with a diode but what about the input circuit?

  • 0
    TI__Mastermind 21336 points

    Hi Shing,

    The bus fault protection of -27 to +40 volts is the DC voltage that the bus pins can handle without being damaged. There are block structures on the bus pins that don't allow this voltage to back feed into the supply of the device.

    The receiver and driver sit in parallel with each other on the CAN bus pins. In the equivalent schematic both output and input pins show the ESD protection circuitry. Does that answer your question?

    Thanks,

    John 

  • 0 in reply to John Griffith
    Intellectual 545 points

    Hi John,

    So in no circumstances the over-voltage (DC or transient) will back-feed into the supply even the over-voltage exceeds the -27 to +40V limits and the device gets damaged?

    Regards

    Shing

  • 0 in reply to Shing Lee
    TI__Mastermind 21336 points

    Hi Shing,

    We cannot guarantee how the device will break if you exceed the absolute maximum ratings of the device. I can guarantee however that if you stay within the absolute maximum ratings of the device the energy on the bus will not back feed onto the VCC2 supply line.

    Thanks,

    John