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TCAN4550: VCCOUT Capacitor with External Transceiver

AP
Intellectual 510 points

Part Number: TCAN4550
Other Parts Discussed in Thread: , BOOSTXL-CANFD-LIN

Hello,

Because of limited PCB space (on a multi channel design) we are wondering about the Minimum 10uF capacitor requirement (i.e. at least 0603) for the VCCOUT pin.

In our design the TCAN4550 will always be programmed to Test Mode and TEST_MODE_CONFIG = 1 (external transceiver). VCCOUT is not used for the external transceiver. According to plan, the only use of VCCOUT is to have a simple resistor divider (say > 10K) to a 3.3V logic input (for additional TCAN4550 state indication, VCCOUT On/Off).

In such a scenario, is it still strongly recommended to have at least a 10uF capacitor on the VCCOUT pin? Should a 4.7uF 16V/25V 0402 work fine as well?

Thanks

  • +1
    TI__Mastermind 36521 points

    Hello AP,

    The majority of the current from the internal 5V LDO will typically be consumed by the internal CAN transceiver when it is used in this mode.  However, it will still be used internally, but the fluctuation in the current will not be as significant as that coming from the internal CAN transceiver driving dominant and recessive bits. 

    I don't have any separate evaluation data with a 4.7uF cap and an external transceiver to definitively state this will be stable under all operating conditions, but it is likely a smaller cap may work when using an external transceiver in test mode. 

    I would suggest that you use a TCAN4550EVM (Link) or BOOSTXL-CANFD-LIN (Link) to help you evaluate your desired hardware and software configuration during your development process.  This would allow you to experiment with different capacitor values.

    Regards,

    Jonathan