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TCAN1042-Q1: Issues related to the rise time and fall time of TCAN1042.

Alan Xia
Genius 10630 points

Part Number: TCAN1042-Q1
Other Parts Discussed in Thread: TCAN1042H-Q1

Hi team,

I checked in other E2E and found that BU gave the min-max of the rise time of TCAN1042 between 28ns and 50ns. As follows:

Customers have encountered the situation that under the conventional can test method, i.e., the CAN side terminal resistance is 120ohm+ the counter side terminal resistance is 120ohm, and the CANH rises slowly than the Vdiff. Please help check whether the rise times of CANH and CANL of 1042 also meet the requirement of <50ns? 

 

 

  • 0
    TI__Mastermind 30710 points

    Hi Alan,

    There is no spec for CANH/CANL single line rise time, what we specify in the datasheet for differential output is just a reference, it's not a parameter of ISO11898-2. Also, we don't specify the max value of rise/time.

    Indeed, there is never requirement for rise/fall time, CAN physical layer only cares about loop delay.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    TI__Genius 10630 points

    Hi Sean，

    The CAN output signal antenna is 32V NG (that is, the host is powered on normally, and CANH and CANL are connected to BATT). The specification indicates that the bus withstand voltage is ± 58V.

    1. Please help analyze why TCAN1044 destroys under this working condition?

    2. Please help confirm whether the TCAN1042 GVDRBRQ1 cannot PASS the 32V antenna test.

    3. Are the rise times of TCAN1042 GVDRBRQ1 and TCAN1044 AVDRBRQ1 the same?

  • 0 in reply to Alan Xia
    TI__Mastermind 30710 points

    Hi Alan,

    Are they connecting both CANH and CANL to 32V simultaneously? This is not a valid test, the short to battery test only consider either of the CAN line is shorted to battery, not both. Also, do they have a common mode choke used?

    The TCAN1042H-Q1 will have a higher bus fault protection up to ±70V, so it will perform better in a short to battery test.

    For the rise time please refer to datasheets of both devices.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    TI__Genius 10630 points

    Hi Sean,

    Pls refer：

    1. If CANH and CANL signals are used as hardwires for the main socket, a single pin is required to perform short BATT experiments, do 1044 and 1042 only support two pins for common short batt?

    2. CAN chip output has common-mode inductance

    3. The working condition is a 24V system. Logically speaking, only a ± 58V CAN chip is needed, and only the equivalent situation with withstand voltage is considered.

  • 0 in reply to Alan Xia
    TI__Guru 64707 points

    Hi Alan,

    We are currently on holiday. Please help give until next week for some feedback, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    TI__Genius 10630 points

    Hi Michael,

    Looking forward to your reply.

  • 0 in reply to Alan Xia
    TI__Mastermind 30710 points

    Hi Alan,

    Alan Xia said:
    1. If CANH and CANL signals are used as hardwires for the main socket, a single pin is required to perform short BATT experiments, do 1044 and 1042 only support two pins for common short batt?

    I'm saying that only single pin is shorted to battery voltage (only one CAN line is shorted to battery voltage, the other is in normal condition), not both pins shorted together to battery at the same time.

    A common mode choke could cause high transient voltage which could be higher than the abs max rating, we have an app note on this:

    https://www.ti.com/lit/an/slla271/slla271.pdf

    Do they have waveforms? And do they have TVS diode placed? If yes, what is the part number?

    Regards,

    Sean