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TCAN1042HV: ACK bit

Part Number: TCAN1042HV

Hi Team,

My customer is using TCAN1042, and now they observe that the voltage level of ACK bit is much higher than other bits, as the waveform shown below.

As I learned from another e2e thread, this might be related to "strong dominant bit" when multiple CAN transceivers source current on the bus at the same time.

However, I would still like to check if the voltage level of ACK bit shown below would have potential risk?

And is there any approach to lower down the voltage level of ACK bits?

  

Regards,

Charles

  • Hi Charles,

    This is expected behavior of the ACK bit. When multiple transceiver drive the bus dominant at the same time, the drive strengths add in parallel to create a stronger dominant signal and a larger differential on the CAN bus. Because this differential is still well within the range for the CAN receivers, there is no issue when it comes to interpreting this bit correctly. There is no added risk to the signal based on this phenomenon.

    Let me know if you have any more questions. 

    Regards, 
    Eric Schott 

  • Hi Eric,

    Thanks for your comment.

    May I know the allowable differential output voltage (dominant) range of the transceiver?

    Regards,

    Charles

  • Hi Charles,

    The differential output voltage that the transceiver is capable of driving is described by the VOD(dom) specification in the datasheet. This output is driven using the Vcc supply of the transceiver so it is not possible for the differential output of this device to be greater in magnitude than this supply. 

     If you mean what differential voltage can be tolerated by these pins, this is the absolute maximum differential voltage between CANH and CANL of ±70V. 

    Let me know if this is the information you're looking for. 

    Regards, 
    Eric Schott