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TCAN1044V-Q1: Schematic Review

Part Number: TCAN1044V-Q1

Hi team,


Requesting a schematic review for this TCAN. Below are my questions and what I found myself.

First, do you recommend swapping to TCAN1044AVDRBRQ1 due to improved emissions? It seems like it's a p2p drop. Please confirm.

TXD

- does this require an external pullup?

RXD

- does this require an external pullup?

- red arrows should be flipped to demonstrate RXD as an output

VCC

- I'm not sure what TC_Vin is, it appears to be connected to a 3.3Vin and 5Vin supply though. I need to confirm this to make sure it's w/in recommended operating range.

STB

- it appears this should be a digital input coming from the can controller. however, I only see that it's pulled up to power. Is this connected properly? 

Thanks,
Lauren

  • Lauren,

    Thanks for bringing this to E2E. I don't see a schematic attached, but I suppose that's because you reviewed it yourself, thanks for the extra help.

    TXD

    - does this require an external pullup?

    RXD

    - does this require an external pullup?

    Neither of these require a pull-up resistor. Placing one will guarantee a state in case the controller leaves the pin floating, and will help rise times when not being driven low, but there are internal pull-ups for this reason as well. Though, the internal pull-ups are fairly weak.

    VCC

    - I'm not sure what TC_Vin is, it appears to be connected to a 3.3Vin and 5Vin supply though. I need to confirm this to make sure it's w/in recommended operating range.

    VCC needs to be 5V with a decoupling capacitor of 100nF close to the pin in the layout.

    STB

    - it appears this should be a digital input coming from the can controller. however, I only see that it's pulled up to power. Is this connected properly? 

    Pulling this up to power will set the device into Standby mode indefinitely, disabling CAN communication. It would make more sense if this were pulled down so it was always in Normal mode, but yes in general this is controlled by an MCU to enable and disable CAN communication when necessary.

    Please let us know if there was a schematic that was supposed to be included.

    Regards,

    Eric Hackett 

  • TIDA-010939_Schematic.PDF

    Hey Eric,

    My mistake for not attaching this!

    Notice we have pullup resistors. From your comment, sounds like it's fine to leave these here.

    For STB- then I believe this is incorrect. I'll let you take a closer look now that you have the schematic. Let me know what corrections should be made.

    Thanks!
    Lauren

  • Eric, gentle reminder on this, thank you 

  • Lauren,

    Is there any control connected to STB as well as the pull-up? If not, the transceiver will stay in Standby mode, not able to communicate, indefinitely. So yes, you are right that it's not correct. This needs to be pulled down or have an MCU connection.

    Regards,

    Eric Hackett