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TCAN1042HGV: Power sequencing requirement for Vcc & VIO ??

Bond - James Bond
Expert 5090 points
Part Number: TCAN1042HGV

One TCAN1042HGV is connected to the CAN bus. When a second TCAN1042HGV is connected to the CAN bus, it drags down CAN HI and CAN LO during it’s power up sequence..

In this implementation during power up the VCC (5V converter) comes up first, then 200ms later the VIO (3.3V converter) powers on. After the 3.3V VIO converter is running, the CAN bus returns to normal.

Are there any sequencing requirements for VCC and VIO on this part?  The data sheet seems to contains no information about this topic?

  • 0
    TI__Guru 53555 points

    Mr. Bond,

    There is not a specific power sequence required for TCAN1042HGV startup. When either Vcc or Vio is powered while the other is under voltage (UV), the device will be in in a Protected Mode with a High Impedance input on the bus (STB must be LOW). In the sequence you describe, I would not expect to see a significant change in bus state until the device powers on into normal mode (Vcc > UVVcc and VIO > UVVIO).

    When the device is in standby mode the bus lines are biased to ground to minimize system supply current. This may cause CANH/CANH to be slightly lower on the bus depending on what other nodes are biasing. What is the state of the STB pin during the power-up sequence? How long after power-up are CANH and CANL dragged down? Scope shots of Vcc, Vio, STB, CANH, and CANL during this time would help diagnose probable cause.

    -Q