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Original question:

TCAN1042H: How is 'BUS Fault' voltage defined?

TCAN1042H: TCAN1042H

Venkataprasad K
Prodigy 30 points
Part Number: TCAN1042H

tHE BUS FAULT VOLTAGE MEANS WHEN THIS VOLTAGE APPEARS ON BOTH THE LINES OF THE COMMON MODE CHOKE ,i ASSUME THIS WOULD BE RELATED TO WITHSTANDING VOLTAGE OF THE TWO LINES OF THE CHOKE  AND NOT WITH RELATED TO THE ACTUAL POWER SUPPLY LINE VOLTAGE.

  • 0
    TI__Guru 53555 points

    Hi Venkataprasad,

    The bus fault voltage for TCAN1042H describes the absolute maximum voltage that the CAN pins can tolerate (+-70V). Any voltage outside of this range may cause damage to the device. This is a single-ended specification meaning it is individual to each CAN pin, not the common mode voltage of the combined CAN lines. This is different from the operational range of the CAN receive which is described is the "common mode range" (+-30V) of the device. This specification is defined by the actual common mode of the CAN bus pins, so it is possible to remain in this range even when one CAN pin is outside +-30V. 

    Neither of these specifications is directly related to the use of a common mode choke. 

    Let me know if this is clear and if you have any more questions.

    Regards, 
    Eric Schott 

  • 0 in reply to Eric Schott1
    Prodigy 30 points

    So in order to suggest a common mode choke, I can take +/-70 v as isolation voltage between two lines or should I take +/-70V as the maximum rated voltage of common mode choke. As you know most of the common mode chokes comes with maximum rated voltage of 50V.

  • 0 in reply to Venkataprasad K
    TI__Guru 53555 points

    Hi Venkataprasad,

    The TCAN1042H transceiver is rated to survive up to +-70V between CANH and CANL (i.e. CANH=+40V, CANL=-30V). Each CAN pin also has a single-ended maximum voltage of +-70V. In Order for a system to take full advantage of this increased range, the common mode choke should also be rated to withstand a absolute maximum voltage of up to +-70V as well as +-70V between the signal lines. 

    If the full +-70V range of TCAN1042H is not required for your application, I would recommend TCAN1044. This device has an absolute maximum CAN voltage of +-58V and will offer better long-term supply capability compared to TCAN1042. 

    Regards,
    Eric Schott