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TCAN330: 3.3V CAN transceiver is having different voltage level during recessive state.

user021864
Intellectual 2145 points
Part Number: TCAN330

Hi, 

My customer is wondering why for the 3.3V CAN transceiver is having different voltage level during recessive state:

For example: 

TCAN330: 

another part is: 

I wonder if this is normal and if there are risk or things to be careful when using two different transceiver together in the same network. 

Please let us know why this is different and what this difference will bring out.

Great thanks for your help. 

  • 0
    TI__Guru 60242 points

    User,

    When the HVD23x series was designed, the thought was to make the 3.3V CAN recessive voltage close to the 5V CAN recessive voltage. While this helped with EMI when using the HVD23x device family on a CAN bus with 5V transceivers, the device alone has less-than-ideal EMI performance because the recessive level is not centered between CANH and CANL.

    The TCAN33x series are our newer 3.3V CAN transceivers, and the recessive level was moved to 1.85V to center it between CANH and CANL to help with individual EMI. When using the TCAN33x device on a CAN bus with 5V CAN transceivers, there can be a chance of EMI performance degradation since the recessive levels are so different, but ultimately it will depend on the design of the bus driver for the individual transceiver.

    So, with the HVD23x series, the individual transceiver EMI is worse due to the recessive level not being centered between CANH and CANL, but is less susceptible to creating more noise on a CAN bus with 5V transceivers. The TCAN33x series has been individual transceiver EMI, but on a bus with 5V transceivers, has a chance to create more noise due to the recessive levels being almost 1V apart. However, for the TCAN33x case, it will depend on how many 5V and 3.3V CAN transceivers there are on the bus.

    Regards,