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About the policing function of LTC4291-1 & LTC4292

Category: Software
Product Number: LTC4291-1 LTC4292

About the policing function of LTC4291-1 & LTC4292

hello

The Police function monitors the power of each port,
Is there a function to monitor the total power of 4 ports?

Looking at the description on page 29 of the data sheet, it seems that the total power of 4 ports is monitored and the power supply exceeding 100W is set so that it cannot be supplied.


Is there a function to set the power threshold of the total of 4 ports?

I would be grateful if you could reply.

Best Regards,
Knj

  • Please request the LTC4291-1 Software Interface datasheet for further details on the software capabilities of the part.

    ADI PoE PSE software files are available for request on Analog’s Software Request Form (http://analog.com/srf).  Fill in the Software Recipient Information and Commercial Information.  In the Software Requested section, select Power over Ethernet in the Target Hardware drop down list and then select the software file(s) for request for the appropriate PSE controller.

  • Thank you for your reply.
    I got the Software Interface Guide, but I think that the Port Policing function is a function to remove the port that exceeds the threshold when the power of each port exceeds the value set from 0x75 to 0x78.

    The data sheet seems to monitor the total power of all ports, but is there a function to monitor the power of all ports other than Port Policing?

    I would be grateful if you could reply.

    Best Regards,
    Knj

  • What I want to do is to monitor the total power of the 4 ports of PSE with the software of LTC4291-1 / LTC4292, for example, if the total power exceeds 120W, I would like to operate to reduce the load.

    Is this possible with software settings?
    Or is it necessary to take measures with an external circuit with some hardware?

    When taking measures with hardware, we are considering the circuit shown in Figure 45 described in AN-105.


    AN-105
    https://www.analog.com/media/en/technical-documentation/app-notes/an-105fa.pdf

    Is it possible to take measures with the above circuit?
    If you have any other recommended circuits, please let me know.

    I would appreciate it if you could reply.

    Best Regards,
    Knj

  • If operating in Semi-auto mode, the host can decide if it has enough power available to power up the PD with the requested class power.  A PSE should not power a PD unless it has enough power available for the power the PD is requesting.  The host can then set the I_CUT and I_LIM accordingly before powering up.  When powered, the LTC4292/LTC4291-1 provides supply voltage, port power and port current readback through I2C.  If a PD exceeds the current limit thresholds longer than the respective timers, the LTC4292/LTC4291-1 will remove power to the PD.  Anything outside of this would require advanced power management from a host controller or external circuitry.