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TCAN1145-Q1: why do I still need standby mode since we already have sleep mode

justifice zhou
Intellectual 400 points
Part Number: TCAN1145-Q1
Other Parts Discussed in Thread: TCAN1044A-Q1

Hi,

I'm not sure in what situation we would need standby mode.

Since sleep mode consumes less power than standby mode, and it can also be wake up through BUS(the same as standby mode).

Then why would we still need standby mode?

  • 0
    TI__Guru 74252 points

    Justifice,

    Standby mode can be used for configuring the device prior to transitioning to Normal mode or Sleep mode. In general, Standby can be seen as more of a transitional mode on a device that also has sleep. This can also be done in Normal mode, but Standby mode would save power in this case.

    Regards,

    Eric Hackett 

  • +1
    TI__Genius 15345 points

    Hello,

    This is a great question. One of the biggest reasons to use a CAN transceiver is it's ability to consume as little power as possible while still effectively communicating with other devices. As you already pointed out CAN transceivers have different "power" modes that consume different amounts of current. By keeping your device in the lowest power state possible you decrease your overall power consumption.

    Now when the device enters sleep mode what is happening is the internal driver and receiver are being powered off and the CAN bus is being biased to GND. This all helps in reducing current consumption. The device then uses a low power receiver to recognize a Wake Up Pattern (WUP). For some of our devices they don't actually require the VCC supply in order to keep this low power receiver turned on. So an additional step you can take to reduce power consumption is to turn off your VCC/VIO supply. Our devices with an INH output will actually do this automatically. What customers do is attach the INH pin to the EN pin of the voltage regulator for the VCC/VIO rail. Automatically the device will turn off the INH pin in sleep mode.

    Now standby is used as a transitionary mode while you are turning on your voltage rails. Keep in mind that most of the time the same voltage rail that is used to power the CAN transceiver is also used to power your MCU. So when your CAN transceiver turns off your voltage rail (using the INH pin) your MCU also needs time to power back on in order to control your CAN device. In this standby state we are waiting for our MCU to turn back on and put our device into normal mode. Not only does this allow us to stay in a lower power state for longer but standby mode also biases your CAN bus to 2.5V. This makes it so that even though your device is not communicating on the bus other devices can continue to communicate with each other.

    We also have other devices that are a lot simpler that don't come with the INH output and their only low power state is standby / silent mode. I recommend looking at the TCAN1044A-Q1. This device is an 8 pin CAN transceiver. It only has a STB pin to control it's state (instead of a STB and an EN pin) so there is only one low power mode that you have to worry about and that is standby mode. The draw back here is that this 8 pin device doesn't have the INH feature or the extremely low power mode of sleep mode which allows you to turn off your VCC/VIO supply.

    Hopefully this makes sense and if you have any further confusion let me know.

    Best,

    Chris