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TCAN4550-Q1: Power Supply Drops to 4.5V Test

Wayne Liu
Expert 8605 points
Part Number: TCAN4550-Q1
Other Parts Discussed in Thread: TCAN4550

Hi,

Because TCAN4550 has the UV definition whose lowest voltage is 4.5V, you know there is a battery voltage drops test for automotive, the drop time from 9V to 4.5V in 10ms, then keep 4.5V for 100ms, then rises 4.5V to 9V in 10ms, how to pass this test for 4550? What I want to do is to add the caps and inductors for the Vbat but I don't how to design the specific values and topology for the caps and inductors, do you have any idea? Thanks. 

  • 0
    TI__Guru 62910 points

    Hi Wayne,

    Given the long duration of the undervoltage condition, it may not be practical to keep the VSUP voltage (and resulting VCC voltage) within its operation limit using just passive components like inductors and capacitors. Is it required for this system to maintain full operation during the battery drop test, or is ok for CAN communication to be temporarily lost at VBAT = ~4.5 V but recover once the full operating voltage returns?

    Max

  • 0 in reply to Max Robertson
    TI__Expert 8605 points

    Max,

    Thanks for your help.

    It requires full operation during drop. This is a general requirement, suggest to consider this in our new products. 

  • 0 in reply to Wayne Liu
    TI__Guru 62910 points

    Thanks, I understand.  Most CAN transceivers have a minimum operating voltage of either 4.5 V or 4.75 V, so supporting a battery drop to 4.5 V (minus a diode drop for reverse polarity protection) can require the use of a buck-boost converter to maintain a stable voltage.  Unfortunately the TCAN4550 uses an LDO to generate the CAN transceiver power rail and so the UV detection threshold needs to be higher accordingly.

    Max