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TCAN4550: Clarification on Power Configuration for TCAN4550RGYR

Banupriya K
Prodigy 90 points

Part Number: TCAN4550

Dear Team,

We are using the TCAN4550RGYR in our device. During power-saving mode, we turn off the IO power (VIO), but there is currently no provision to turn off the supply power (VSUP).

Could you please confirm whether it is acceptable to proceed with this configuration, or if the supply power also needs to be turned off to avoid any potential back-drive issues?

Note :

Supply power (VSUP) = 12V

IO power (VIO) = 3.3V.

Attached is the circuit for your reference.

image.png

Please provide your input on the same.

Thanks & Regards,
Banupriya K

  • 0
    TI__Mastermind 38191 points

    Hello Banupriya,

    It is expected that VSUP remains on while the device is in Sleep Mode so that it can monitor for a Wake Up Event.  The internal LDOs are disabled in this mode and only a small detection circuit looking for a Wake Up Pattern (WUP) on the CAN bus, or a local wake up (LWU) which is a voltage change on the WAKE pin remains active.  

    I'm not sure what type of back-drive issues you are referring to, but I would say no, there is not a problem with keeping VSUP on.

    I see in the schematic that both the INH and WKRQ_N are left as no connects.  This is fine if they are not used, but these are the two pins used to signal the device has seen a wake-up event and transitioned from Sleep Mode to Standby Mode. So I'm assuming you are not expecting to use the TCAN4550 for any form of wake-up detection,

    If you do a revision to the board, I would recommend placing a series resistor between the OSC1 pin and the crystal which is referred to as a dampening resistor and can be used to help adjust the amount of current flowing to the crystal and optimize the performance.  Please see the TCAN455x Clock Optimization and Design Guidelines Application Report (Link) for more information.

    The INT_N pin is an open-drain and requires a pull-up resistor to VIO which is not shown in the schematic.

    The GPIO1 pin is not an open-drain so it does not require a pull-up resistor unlike the GPO2 pin that is an open-drain that requires a pull-up resistor to VIO.

    Regards,

    Jonathan