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TCAN337: RXD pin problem

DELMAS Yannick
Intellectual 320 points

Part Number: TCAN337

Hello,

I use a TCAN337 on a custum board with a STM32 µC. I have about 300 custums boards, and on 4 of their, I have to change the TCAN337. The RXD line is to 0V instead of 3.3V.

Have you an idea where the problem can be come ?

Best regards.

  • 0
    TI__Guru 74552 points
    Delmas,

    Is there any way a schematic can be shared? And if you try to send a signal on the TXD pin, does the RXD pin respond?

    I'd like to make sure that the VCC pins are still supplied on these devices, and the state of the FAULT pin, is it possible to check this?

    Regards,
  • 0 in reply to Eric Hackett
    Intellectual 320 points

    Hello,

    I forgot to say. At the beginning, all the boards work's fine.

    But after some use, and connect/disconnect on CAN1 or CAN2, I have the problem.
    I send you the schematic.I'm sure that the VCC pin is OK, but I don't verify the Fault pin, and I don't send on TXD pin.

  • 0 in reply to DELMAS Yannick
    TI__Guru 74552 points

    Delmas,

    Thank you for the information, it's good to know that they worked fine at some point, that may point to some kind of EOS damage. When you're disconnecting and reconnecting at CAN1 and CAN2, are the transceivers powered on?

    Do you mean you have never sent any messages on the TXD pin, or you haven't tried it since they became faulty? Let me know if you can check the FAULT pin and the function of the TXD pin.

    Regards,

  • 0 in reply to Eric Hackett
    Intellectual 320 points

    Hello,

    Yes I think the problem is EOS or ESD. Yes when I connect/disconnect CAN1 or CAN2, the transceivers are powered on. But I don't see perturbation voltage on the VDD.

    I haven't any boards whit the defaut, I replace all of them. So I can't look the TXD and FAULT pin until I have an other problem.

    But, how can I protect the CI for the EOS ? I have a filter and a NUP2105LT1G CI protection on the bus CAN.

    Best regards.

  • 0 in reply to DELMAS Yannick
    TI__Guru 74552 points
    Delmas,

    The filter and protection diode you have on there should be enough, the diode looks like it is specified perfectly for this application. You could add a bit more capacitance to GND to help with slowing down the rising edge of the EOS events, but you have to be careful about how much is added, because it could warp the CAN signals too much to be read correctly.

    Regards,