• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 538 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS23861: ICUT current limit encoder (type 1)

james Kirkman
Prodigy 80 points
Part Number: TPS23861

How does the ICUT current limit encoder (table 15) of TPS23861 datasheet relate to the different POE classes. I am looking at adding class protection so that a class 1 device is unable to pull more than its class current. as i understand class 1 can supply up to 4W from the PSE, The spec voltage range at PSE is 44 -  57V (im using 48V) this means that class one can pull 70mA to 90mA which is not an option in the table. 

Thank for your help.

  • 0
    TI__Intellectual 1695 points
    Hi James,

    If you configure TPS23861 in auto mode, the ICUT current will be set automatically according to the class result. But if you configure TPS23861 in semi-auto or manual mode, you have to set the ICUT current through MCU via I2C.
    The minimum ICUT current is 110mA, you can't specify to 70mA-90mA. But you can use MCU to monitor port power by read the port voltage and current to implement software protection.

    Thank you
    Best Regards
    Jack Chen
  • 0 in reply to Jack CCY
    Prodigy 80 points
    Hi

    Could you clarify this because i have plugged in a class 1 device into the IC in auto mode and measure 200mA at 48V this is both above class power limit and ICUT current limit (if set to 110mA).
    does the IC in auto mode only set the ICUT limit for the device type e.g 374mA for type 1.
    I guess my main questions is where are the table values derived from (110mA, 204mA, 374mA) as i do not find they line up with the POE classes.

    Thanks
  • 0 in reply to james Kirkman
    TI__Intellectual 1695 points

    Hi James,

    In auto mode, when class 0, 1, 2 and 3 (Type 1) PD is plugged in, the PSE will set the ICUT to 374mA automatically.

    If you would like to use 110mA you have to use MCU to configure it.

    And the table values derive from the customers' common use.

    Thank you

    Best Regards

    Jack Chen