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TPS23753A：Hardware Classification and the CLS pin

taka1
Prodigy 30 points
Other Parts Discussed in Thread: TPS23753A

HI

We got a question about TPS23753A.Could you help us?

[Question]

As we know,POE Hardware classification allows a PSE to determine the power requirements of a PD before starting, and helps
with power management once power is applied.In TPS23753A，We populate the CLS pin with 90.9 ohms resistor，and founded that
it's still working while the load of PD is not reached  6.49W.Is that right?In my submission,when use CLASS 3,the load of PD
must between 6.49W and 12.95W.otherwise,it wouldn't work.

Best Regards,

  • 0
    TI__Genius 9230 points
    Hi Taka,

    These minimum & maximum power requirements are only recommendations for which class to choose. The PSE will not disconnect if, for example, you fall under 6.49W when configured for class 3. However, you must stay under the maximum power (12.95W) to stay connected.

    There is a minimum amount of input current that must be drawn by the PD for the PSE to stay connected. This is know as the Maintain Power Signature (MPS) and is detailed in section 8.4.5 of the TPS23753A datasheet. If your PD draws less than this amount (in your case, 10mA DC), then the PSE will disconnect power.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer