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[FAQ] TPS23881: Is the TPS23881 interoperable with non-compliant "Class 5" devices that were designed to receive >25.5W prior to the IEEE 802.3bt standard?

Intellectual 1580 points

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Part Number: TPS23881

Is the TPS23881 interoperable with non-compliant "Class 5" devices that were designed to receive >25.5W prior to the IEEE 802.3bt standard?

  • Prior to the IEEE 802.3bt standard, some PD devices elected to use an elevated (i.e. “Class 5”) classification current to identify themselves as non-standard loads capable of drawing > 25.5W (Class 4 –Type 2).These devices are sometimes called "Class 5" devices which are NOT the same as IEEE 802.3bt compliant class 5 devices. IEEE 802.3bt compliant Class 5 devices present two different classification currents: Class 4 (40mA) on the first two class fingers, and Class 0 (<5 mA) on the 3rd and 4th class fingers. Non-compliant Class 5 devices present 50+ mA during classification which is non-compliant to the IEEE 802.3bt standard.

    The TPS23881 can power up non-compliant Class 5 devices, however, since they are non-compliant they need to be powered from manual mode using host (I2C) control. Please see the slides below which go over how to use the TPS23881 GUI to power up non-compliant "Class 5" devices:

     

    Best Regards,

    Brett Colteaux

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