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Original question:

ISO5452-Q1: Can RDY and FLT be connected together?

UCC21750-Q1: Can RDY and FLT be connected together?

Hung Ching Hsu
Expert 3086 points
Part Number: UCC21750-Q1
Other Parts Discussed in Thread: UCC21736-Q1

Hi Team, 

My customer is considering UCC21736-Q1 and UCC21750-Q1. 

They don't have enough GPIO for their MCU, so they want to know if RDY and FLT can connect together and connect to MCU to save GPIO. 

Could you help confirm? Thanks.

Regards,

Jo

  • 0
    TI__Expert 3860 points

    Hi Jo, 

    Since both RDY and nFLT are open-drain pins, the customer can connect these two outputs together. We suggest using one 5kOhm resistor for both pins.

    The downside would be that if the connected pin is pulled low, customer wouldn't know whether the RDY pin or the nFLT pin is pulling it low. 

    Thanks, 

    Vivian

  • 0 in reply to Vivian Qi
    TI__Expert 3086 points

    Hi Vivian, 

    Thank you for the reply! 

    May I know what this 5kOhm is for? 

    And want to confirm, where should customer add this resistor? Add it to both pins respectively and then connect to CPU or only one between CPU and where after these pins connected?

    Vivian Qi said:
    We suggest using one 5kOhm resistor for both pins.

    Thanks.

    Regards,

    Jo

  • +1 in reply to Hung Ching Hsu
    TI__Expert 3860 points

    Hi Jo, 

    The 5kOhm resistor would be the pull-up resistor for these pins since these pins are open-drain. Use only one 5kOhm resistor; one side of the resistor connects to VCC and the other side connects to both RDY and nFLT as well as the CPU. 

    Thanks, 

    Vivian