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TCAN1043-Q1: VIO supply from CPU IO port

NOBUO FUJIHARA
Genius 9355 points
Part Number: TCAN1043-Q1

Hello,

My customer wants to configure VIO and VCC with following condition.

VCC : 5V supply from LDO

VIO : 5V supply from GPIO of CPU

Assuming GPIO drive availability is enough to supply VIO, is there any concern to use TCAN1043-Q1 with above configuration?

Best regards,

Nobuo

  • 0
    TI__Guru 74282 points
    Fujihara-san,

    There is no problem with this configuration, as long as all supplies share the same GND, the device should work fine in this configuration.

    Regards,
  • 0 in reply to Eric Hackett
    TI__Genius 9355 points

    Hi Eric-san,

    Thanks for your reply.

    Customer still concerns because there will be slight voltage difference between VIO (suppled from  CPU) and VCC (supplied from LDO).

    Woule you confirm by taking account above codition?

    Best regards.

  • 0 in reply to NOBUO FUJIHARA
    TI__Guru 74282 points
    Fujhara-san,

    VIO is the internal pull-up source for TXD, and VCC is the supply for the biasing unit of the bus, so I don't foresee a voltage difference (if slight) causing any issues.

    Does the customer have an idea of what the difference will be between the two source? Just to verify I want to test this condition in the lab.

    Regards,
  • 0 in reply to Eric Hackett
    TI__Genius 9355 points
    Hi Eric-san,

    Thanks for your dedicated support.

    As power-up/down sequence customer is planning to apply below.
    Power_on: VIO turns on, then VCC turns on
    Power_down : Vcc turns off, then VIO turns off
    Difference in voltage between VCC and VIO would be less than +/-0.3V.

    Best regards,
  • 0 in reply to NOBUO FUJIHARA
    TI__Expert 3810 points
    Fujihara-san,

    I just wanted to follow up on this as a confirmation. We tested in the lab the device according to the power-on and power-down steps that you specified. I tested the following conditions:

    VIO=4.7V and VCC=5V
    VIO=5.3V and VCC=5V
    VIO=5V and VCC=4.7V
    VIO=5V and VCC=5.3V

    The device performed as normal in all of the described conditions. The slight difference in voltage as a matter of fact didn't affect the communication. The only visible effect were that by changing VIO, the RXD signal was very slightly decrease or increased depending on VIO value; by changing VCC instead it was the CANH and CANL who were slightly increase or decrease in value, but all this is normal as Eric explained previously. VIO is connected to TXD and RXD, while VCC supplies the bus.

    Let me know if this makes sense or if I can help in any other way.

    Thank you and best regards,
    Adrian
  • 0 in reply to Adrian Ymeraj
    TI__Genius 9355 points
    Adrian-san,
    Thanks a lot for your support!