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TCAN1051HV: TCAN1051 CAN transceiver doubt, 'S' pin

Jeferson Pehls
Expert 1170 points
Part Number: TCAN1051HV
Other Parts Discussed in Thread: TCAN1051, SN65HVD230, ISO1044

Hi.

Currently we are using CAN transceiver SN65HVD230 with success, and we want to substitute it by a TCAN1051 on the next PCB layout because it is 'fault-protected' and withstands more voltage on the bus lines H and L, we would select a part number which supports +-70V.

I have a doubt about TCAN1051, exactly regarding the pin 'S' that selects Normal Mode or Silent Mode. As we don't have any free GPIO pin on the microcontroller that is an ESP32-WROOM module, we can't control 'S' pin through it, and I would connect 'S' pin directly to GND, in order to set the Normal Mode constantly on the TCAN1051. My doubt is, if I do this, will the TCAN1051 be driving the bus constantly in a manner it will interfere in the communications of the remaining devices on the bus?

And also, I would like to ask if there is some transceiver from TI that withstand +-70V on the bus pins, and that are pin-to-pin compatible with SN65HVD230? That works exactly or very similar as SN65HVD230 but that is fault-protected? +-70V?

Regards,
Jeferson.

  • +1
    TI__Guru 53555 points

    Hi Jeferson,

    Good question here. While any CAN transceiver is active (in Normal mode) and driving a recessive state (logic 1) on the bus, it is only weakly biasing both CANH and CANL to a recessive level voltage (commonly Vcc/2). This is actually beneficial to the rest of the network with any actively transmitting nodes, as it stabilizes the common-mode of the bus. Any node that is actively driving communication (both recessive and dominant states) will easily overpower this weak bias so that the desired signal can be propagated on the bus. So in reality, leaving the TCAN1051 in Normal mode constantly will be more beneficial to the bus overall, so tying the S pin low (always on) is no issue. 

    Either the TCAN1051 which you've identified or the Standby mode version, the TCAN1042, would be the best solutions here that offer the +-70V bus fault protection. Because these are 5V supplied CAN transceivers, there will inherently be differences from the 3V supplied device you're moving from. However, the majority of 3V CAN transceivers today (including SN65HVD230) attempt to conform to the ISO 11898 CAN standard followed by 5V supplied transceivers, so I would expect similar if not improved performance when switching to TCAN1051 on an ISO compatible network. 

    Let me know if you have any more questions.

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    Expert 1170 points

    Hi Eric, thanks very much.

    I saw TCAN1051 meets the ISO 11898-2 and can withstand to +-70V on bus lines for H suffix, we already have 5V on the PCB, and we will connect 3.3V supply to VIO pin in order the interface with the MCU will be 3.3V levels, TCAN1051 is just not isolated but we think that's not needed, so I think TCAN1051 will really be the next choice.

    Regards,

    Jeferson.

  • 0 in reply to Jeferson Pehls
    TI__Guru 53555 points

    Hi Jeferson,

    Glad to hear this is looking like a good solution. 

    Because you mentioned isolation, I'll also point out that we offer digital isolators with integrated CAN transceivers. An isolated version of the TCAN1044 for instance would be the ISO1044 (supported by our ISO product line, but of course we can still help with the CAN-specific questions). This would be good to promote if it turns out that isolation is indeed required here. 

    Regards,
    Eric Schott