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TCAN1044-Q1: Bus voltage in standby mode ?

Lee, Sam
Expert 6065 points
Part Number: TCAN1044-Q1

Hello team,

 

Can I ask about the bus voltage of CAN transceiver on the following condition?

 

Assumptions:

-. 10 nodes with TCAN1044-Q1

-. 1 node (CAN#1) is in normal mode (no data control, no WUP)

-. The other 9 nodes(CAN#2~#10) are in standby mode.

 

Questions:

-. What is the bus voltage on CAN#1? Is it in Recessive (CANH/L = 2.5V), or other voltage?

-. What is the bus voltage on CAN#2~#9? CANH/L = ?

       : Is the bus in standby mode pulled down to GND?

       : As the number of nodes increases, is the bus voltage getting lower, due to one recessive voltage and the other pull down nodes?

 

Thanks,

Sam Lee

  • +1
    TI__Genius 15345 points

    Hi Sam,

    Firstly, you should be using the TCAN1044A as that device has better ESD protection.

    Lee, Sam said:
    -. What is the bus voltage on CAN#1? Is it in Recessive (CANH/L = 2.5V), or other voltage?

    When the TCAN1044 is in standby mode the bus is biased to GND. So CAN#1 would see the other 9 devices biasing the bus to GND and it would see a GND on the can bus:

    Lee, Sam said:
    -. What is the bus voltage on CAN#2~#9? CANH/L = ?

    They are GND as well. Keep in mind that all of these devices have their CAN pin tied together so they would always see the same bus bias excluding any ground shifts.

    Lee, Sam said:
           : As the number of nodes increases, is the bus voltage getting lower, due to one recessive voltage and the other pull down nodes?

    The recessive bias is very weak, the GND bias is much stronger so it will always see a ground even with many devices with a recessive bias. Now one device may have a ground shift compared to another but excluding the ground shifts everything will stay at essentially 0V.

    Best,

    Chris