• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 34 subscribers
  • Views 2713 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCAN332: Mixed system that 3.3V CAN(TCAN332) and 5V CAN.

Tetsusei Kan
Prodigy 180 points
Part Number: TCAN332

Hi,team.
I'm evaluatingTCAN332DCN in a mixed 3.3V and 5V CAN system .
I use 5V CAN IC that HA13721 or R2A25416 etc.
I use single termination.
Probing CANH with an oscilloscope , CANH has large linging at end.

I assumed that I could 3.3V CAN can mix in 5V CAN system , but dose it have any restrictions?
For example node amount,bus length...

I post measured waveform and block diagram.

  • 0
    TI__Intellectual 2090 points

    Hello,

    Normally, 3V CAN and 5V CAN do not mix on the same system.  This is due to the face that recessive levels are driven differently between the two VCC supplies.  For 3V CAN, the recessive level will be 3.3V/2 = 1.65V, and for 5V CAN, the recessive level will be 5V/2 = 2.5V.  This can cause communication issues and electromagnetic performance issues in applications.

    I haven't seen an issue like the one you show in the scope shot.  Do you know which transceiver is driving the bit pattern shown?  Is it a 5V CAN transceiver or a 3V CAN transceiver?

    For what reason do you implement a 3V CAN transceiver for that node?  TI has a portfolio of 5V CAN transceivers that are able to support 3.3V VIO logic to the microcontroller, such as the TCAN1042V.

    Thanks,

    Max Megee

    TI Transceiver Interface

  • 0 in reply to Max Megee
    Prodigy 180 points

    Hi,Max.

    The purpose that we use 3.3V CAN is reducing power consumption.

    we asked before in E2E this question through yoshida-san.
    e2e.ti.com/.../2811128
    And we read  Application Report:SLLA337 'Overview of 3.3V CAN Transceivers' before .
    so we thought '3.3V CAN and 5V CAN are able to mix.'

    Explain scope shot , this waveform drived by 5V CAN tranceiver probably.

    we want to use CAN with 3.3V MCU and reduce power consumption . This is a request for products that to be made from now on.
    but we want connect 5V CAN module (legacy product) too.
    Which IC should I use?

    thanks.

  • 0 in reply to Tetsusei Kan
    TI__Intellectual 2090 points

    Hello,

    Apologies, let me amend my above comments.  

    The 3.3V CAN and 5V CAN transceivers may operate without communication issue on the same bus network.  The transceivers that you have chosen should operate together. The drawback to mixing 3.3V and 5V CAN networks is that the recessive levels will not be the same reference, and you may see more noise on the common-mode.  But if your application allows it, 3.3V CAN certainly may provide lower power consumption.  And it doesn't look like the issue in these signals is related to common-mode noise.

    I am wondering if this signal behavior is due to an over-voltage stress or small ESD event.  Can you provide some more information about the application and environment in which these transceivers are operating?  Do you see this issue on every CAN transmission?  Is it repetitive behavior, or inconsistent?

    Best Regards,

    Max

  • 0 in reply to Max Megee
    Prodigy 180 points

    Hi,Max.

    Thanks for your answer.

    While waiting for your answer, we discussed with Mr. Yoshida, who belongs to TIJ.
    Then, we examined within the team and decided that the mix of 3.3V CAN and 5V CAN was risky.
    A certain combination is a normal communication waveform, but a certain combination produces an abnormal communication waveform.
    This is a reproducible result.
    Therefore, I decided to shift to the examination of TCAN1042.

    Thanks.