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TPS23880: disable and re-enable a single port with 1A current limit.

Jerry Chen
Expert 5110 points
Part Number: TPS23880
Other Parts Discussed in Thread: TPS23881

Hi there,

I used below programming to make 90W for each port. I found the last four programming statements should follow the order,  otherwise, the current limit is only 420mA, not 1A.  At this time, after disable then enable a single port with Reg_0x19, the current limit changes from 1A to 420mA. If I re-program it by the same programming, it would disable other ports. How could I just re-enable this port with 1A capability?

Thanks.

tst_poe_write 1,0x12,0x55  //Manual mode

tst_poe_write 1,0x29,0xff  //Choose 4 pair 90W

tst_poe_write 1,0x13,0x00  //Disable DC disconnect

tst_poe_write 1,0x14,0xff  //enable detection and classification

tst_poe_write 1,0x19,0xf0  //Close all ports

tst_poe_write 1,0x40,0xf0  //Select 2x foldback, 1A for each port

tst_poe_write 1,0x55,0xff  //select alternative foldback

tst_poe_write 1,0x19,0x0f  //Open all ports

  • 0
    TI__Genius 15685 points

    Hi Jerry,

    Are you trying to turn on TPS23880 ports with nonstandard PDs? If the PDs are standard, you should use auto mode or semi auto mode. The manual mode is designed to turn on non IEEE compliant PDs. 

    In semi auto and auto mode, the ILIM(0x40) and 4P PCUT(0x2A and 0x2B) will be set automatically based on the PD class level. You only need to issue turn on command through register 0x19. 

    In your case, I think the issue ( "it would disable other ports") is caused by your 5th command: tst_poe_write 1,0x19,0xf0  //Close all ports.

    In addition, TPS23881 is the newer BT SE device with autonomous mode, reduced Rsense. If you just want to set all ports to 90W for standard applications, you can just configure the AUTO pin resistor to 90W and the ports will be operating at 90W automatically without any host control. Thanks.

    Best regards,

    Penny

  • 0 in reply to Penny Xu
    TI__Expert 5110 points

    Hi Penny,

    The PDs are not standard. In fact, they used TPS23880 as 8 port 90W hot swap/load switch. What is your advice for this application?

    Thanks.

  • 0 in reply to Jerry Chen
    TI__Genius 15685 points

    Hi Jerry,

    What kind of nonstandard PD are they connecting to? Does the PD present valid detection and classification signature? 

    I would recommend to switch to TPS23881 as it has reduced Rsense to reduce the power loss. In addition, TPS23880/TPS23880 can't support eight 90W ports as you will need to combine two PSE channels to support one 90W port. So one TPS23880/TPS23881 device can support four 90W port. Thanks.

    Best regards,

    Penny

  • 0 in reply to Penny Xu
    TI__Expert 5110 points

    Hi Penny,

    The PD is just a load. Customer just used TPS23880 as 8 port hot-swap/load switch.