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SN65HVD231: Allowable voltage on CANH and CANL when part is not powered

Barney
Prodigy 230 points
Part Number: SN65HVD231
Other Parts Discussed in Thread: SN65HVD230, SN65HVD230Q-Q1, , SN65HVDA100-Q1

What is the maximum allowable or safe voltage on CANH (pin 7) and CANL (pin 6) when the part is not powered (Vcc = 0V) for part SN65HVD230 or part SN65HVD231?

  • 0
    Guru 266150 points

    These limits are listed in the Absolute Maximum Ratings table (section 8.1 in the datasheet): −4 V to 16 V.

  • 0
    Prodigy 230 points

    Sorry, my mistake on the question.

    The parts I am looking at include the SN65HVD230Q-Q1 and the SN65HVD231Q-Q1 (I was not aware of the very similar part you were referencing in your answer).

    However, the absolute maximum table is not clear about the conditions under which the ratings are valid and neither are the recommended operating conditions (I'm really interested in safe operating levels not maximum levels).  The recommended operating conditions as listed on page 6 of the datasheet say voltage at any bus terminal should range between -2.5V to 7.5V.  But the datasheet does not indicate if these voltage levels are valid for all supply voltage levels (in this case Vcc = 0V).

    So the question remains, what is the allowable range of safe voltage levels on CANH and CANL when Vcc = 0V?

    Thanks

  • 0 in reply to Barney
    Guru 266150 points

    All recommended operating conditions must be met for the device to work correctly (with the specified electrical characteristics).

    VCC = 0 V is outside the recommended operating conditions. There is no safe operating level because the device is not operating.

    At VCC = 0 V, the only question is whether the device might be damaged. To prevent that, you must stay inside all absolute maximum ratings.

  • 0 in reply to Clemens Ladisch
    Prodigy 230 points

    Thanks, but this is still not totally clear.

    I never said I want the part to operate when Vcc = 0V, naturally its not operating because it is powered off (Vcc = 0V).  My question is for a part that is not powered on but is connected to active CAN data bus lines, what voltage levels can be present on the CANH and CANL pins so no damage is done to the part?  This seems like a clear question.

    The power to the part will be ON or OFF at various points in time, so I want it to work when it is powered ON and not incur damage when it is powered OFF and exposed to CAN bus voltages.  Note that one of the FEATURES on page 1 says "Unpowered Node Does Not Disturb the Bus".  This feature seems to suggest that it is OK to have an unpowered transceiver on the bus with the CANH and CANL pins exposed to voltages on the CAN bus lines.  Is this correct?

    Your answer says that at Vcc = 0V, the voltage at CANH and CANL must stay within the absolute maximum ratings.  This implies that for a part that is not powered on (Vcc = 0V), the voltage levels on CANH and CANL can range from -7V to 16V and NOT cause any damage to the part.  Is this correct?

    Thanks

  • 0 in reply to Barney
    Guru 266150 points

    Yes, your question is answered by the absolute maximum ratings table.

  • +1 in reply to Barney
    TI__Mastermind 25105 points

    John,

    Regardless of whether the device is powered, the ranges of the Absolute Maximum Ratings tables apply. For certain devices that have restrictions based on the supply, you would see a reference to this in that very table.

    For example, the SN65HVDA100-Q1 (older LIN transceiver unrelated to this exact question) has an absolute maximum rating for its INH pin of VSUP + 0.3 V.

    The ratings for the SN65HVD23x and SN65HVD23x-Q1 are valid as long as all absolute maximum values are met. Supply voltage of 0 V is within this range, so the other absolute maximum ratings are still valid.

    Best,

    Danny