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TCAN1043-Q1: Low power mode

Shirley He
Expert 5475 points
Part Number: TCAN1043-Q1
Other Parts Discussed in Thread: TCAN1043

Hello,

Does TI have any CAN transceivers with the low power mode that both driver and receiver are turned off and the bus is not pulled down? For TCAN1043, it seems that the silent/standby/sleep mode all cannot meet my requirement.

Here is what I need to do. I am going to use several CAN transceivers on one CAN bus. But not all the devices are going to work at the same time. Sometimes just one of the device needs to work. For the other devices, the receiver should be disabled. But meanwhile, the CAN bus cannot be pulled down (which is standby mode as far as I understand). Is there any way to realize this?

Thanks in advance!

  • 0
    TI__Guru 74292 points
    Shirley,

    Just to clarify, by pulled down you mean the bus is at 0V?

    With any of our CAN transceivers that have Sleep/Standby/Silent mode, the CAN bus will not be pulled down while they are in these states. While RXD may be low, the CAN bus will remain recessive (~2.5V). When they are in Low power mode, they are meant to not be noticed on the bus and consume as little current as possible, while still monitoring the bus for a wake-up request. When they are in these low-power states, the receiver is only enabled to detect and notify of a wake-up request, not to drive traffic from the bus.

    The function you are describing with some devices on and others in a low-power mode, this is called partial networking. This function is typically realized by the wake-up requests have an identifier associated with them so only certain devices connected to the bus wake up while the others stay in the low-power state. Unfortunately we don't have any devices available to sample that allow for this function, however we do have one device in development, and another family of devices getting kicked off that will serve this function.

    Can I get a little bit more detail of your application? There may be another way we can realize this type of system, for instance powering down the CAN node as opposed to leaving it on in a low-power mode. This isn't ideal, but it may still work.

    Regards,
  • 0 in reply to Eric Hackett
    TI__Expert 5475 points

    Hi Eric,

    Thanks for your prompt and detailed explanation.

    It can be seen from the figure below that Bias unit switches to GND at standby mode. That is why I thought it will pull down CANH and CANL. Not necessarily to 0, but with some pull down ability. It that correct?

    I also see the same result in my test. If all transceivers are at normal modes, below is the waveform of the bus. But if one of the devices is at standby mode, the bus bias is reduced to lower than 2V, as shown below. So what do you mean by the CAN bus remains recessive at standby mode? And I think the waveform is not acceptable, right?

    Sorry I am  new to the interface products and please correct me if I misunderstand anything.

     

  • 0 in reply to Shirley He
    TI__Guru 74292 points
    Shirley,

    You are correct in that the CAN bus will be weakly biased to GND, and there should be a decaying value of the recessive level on the bus, but I wouldn't expect it to drop as low as it does. What is the data rate you are using and is there any chance you can share a schematic of the board this device is on?

    Regards,