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TPS23881: 2P Police ignore above 22W in Diagnostic/Manual Mode

Stephane BOCH
Prodigy 90 points
Part Number: TPS23881

Hi,

I am using channel 1 in 2 pairs Diagnostic/Manual Mode but 2P Police register value is ignored above 22W and the channel is indeed not able to source more than 22.3W. I would like to source 30W.

Please find below the register configuration that is proceed:

Power Allocation (@0x29) - 4PWM12=0   MC12=0b011 (2-Pair 30W)

Operating Mode (@0x12) - C1Mx = 0b00 (Off Mode for channel configuration reset)

Operating Mode (@0x12) - C1Mx = 0b01 (Diagnostic/Manual Mode)

2P Police 1 (@0x1E) = 60 (30W)

Disconnect Enable (@0x13) - DCDE1=0 (DC Disconnect Disabled to maintain power)

Power Enable (@0x19) - PWON=1 (turns on channel 1)

It perfectly works below 22W and I am able to change the power limitation up to 22W but not above.

What did I miss ? 

Stephane

  • 0
    TI__Mastermind 41760 points

    Hi Stephane,

    Thanks for your question. Are you planning to operate your design completely in manual mode or just for evaluation purposes? 

    I will forward the SW related question to our SW/FW apps engineer. Thanks!

  • 0
    Prodigy 90 points

    Hi Darwin,

    The application is a PoE switch. Each port can be configured to run in 802.3at mode or in "forced" mode for 802.3 non compliant PD device.

    So I need the manual mode.

    By the way, I am using the TPS23881 evaluation board so it is not an hardware issue.

    Best Regards

    Stephane

  • 0
    TI__Expert 5330 points

    Hi Stephane,

    Thanks for providing the details of your setup.  I will see if I can recreate this setup on our EVM in the lab on Monday and let you know what results I get.

    Regards,

    Steve

  • 0
    TI__Expert 5330 points

    Hi Stephane,

    I believe that you are tripping the current foldback protection.  The default setting for the foldback is 400 mA.  In automatic mode it is automatically updated to 1.2A whenever a class 4 or higher port is negotiated.  

    If you are using the GUI, you can click on the RJ-45 icon for the channel you are using and select "2x Foldback Selection" in the menu that comes up.  If you are programming using the registers, please set the appropriate bit (by channel) in Register 0x40 [7:4].  

    Regards,

    Steve

  • 0 in reply to Steve Preissig
    Prodigy 90 points

    Hi Steve,

    It was indeed the 0x40 register : issue solved ! 

    Thanks a lot.

    Best Regards,

    Stephane